let's talk about mike's behaviour throughout s3-s4 and why he's not just an asshole. first off, i need to express how very 14 years old he is. he's SO 14. were any of you normal at that age? no, and if you say yes you're lying. he's doing so much better than most would, especially as a young teenage boy in the '80s from an emotionally repressed household with a shitload of trauma about losing people, depression, shutting down as a coping mechanism, probably autism, a desperate desire to be normal and grown up, and a terrible mindset in which his worth, as a child hugely out of his depth, is entirely based on being able to save and take care of people.
mike's behaviour in s3 goes hand-in-hand with the fact that he sees will as not wanting to grow up. read it as "it's not my fault you're falling behind and stuck in childhood while we all grow up" instead of "it's not my fault you're gay", which he doesn't know, and it all makes sense. mike frames everything as what they’re SUPPOSED to do — "we're not kids anymore", he says. he’s been made to get rid of old toys, they’re getting older, they’re supposed to get girlfriends and put aside games, the other boys are always talking about hot girls and lucas and nancy said he like-likes el and then he lost her and crammed all that guilt and grief inside, and now he’s got her back, so things have to be perfect.
anyway. for a straight or gay kid this is a weird time full of pressure. he's trying to be in a grown-up relationship when all he needs is to be a kid, and he's positioned himself as the boyfriend and, in the first season, the caretaker of el — he needs to be needed and feels worthless when he's not taking care of everyone. add that to the fact that he and the others are all traumatized by something that forced them to be much more mature than they should be (most of all will — one of the reasons why he’s so desperate to play d&d and go back to normal. it’s not [just] about being gay while your friends get girlfriends, but mike just saw this "childish" behaviour and didn't understand, or couldn't face, the why), and how mike was always soft for will, always a safe space, but he started to be scared and intensely protective in a new way due to their trauma — after s1 he was aimless until will was in distress, and now mike had someone to save again — except now things are normal and he's supposed to be normal and caring that way isn't normal (from "i'm the only one acting normal! i'm the only one who cares about will" to shoving him away and acting like he's ignoring him all the time), and you'll see that of course he overcompensates. with all of this going on, it makes sense that mike’s struggling to grow up the way he feels he must.
this is why will scares him — mike spits at him that he can’t possibly expect to sit in the basement and play games and never grow up and be together for the rest of their lives (because that’s not what they’re supposed to want) and will… says he DOES want that. he’s able to admit something that makes mike feel inadequate and immature, and possibly a bit broken. that’s threatening to mike, who’s not quite so good at breaking out of conformity, free of expectations. though he never respected them, he started internalizing them anyway. like when his father fixes mike's tie — it chokes him, and ted says it's supposed to. but this is why his return to d&d at the end of the season is significant — it marks him embracing his identity, his interests, his passions again, letting himself exist rather than trying to grow up too fast and be someone he’s not. even then, he's still embarrassed about it once he's with el (but not when he's with will), saying "sorry. that made me sound like a seven-year-old" after expressing excitement about christmas presents, though el does nothing to make fun of him and most likely has no real concept of this stuff being humiliating anyway, meaning he's enforcing this shame on himself and on her. maybe he's simply nervous around her, but it's interesting. and she does often seem disinterested in the things he likes, or like she's tolerating it. (it's also why it's interesting that when will brings it up again — getting rich, never working again, just playing nintendo together for the rest of their lives — mike says YES this time. maybe it's just a fantasy, but to mike, he hopes it's a possibility: "i wanted this then, and i still want it now. do you?" "yeah, i do. i always did.")
now, all of this makes the “mike’s trying to be as normal as possible” stuff in season 4, the “shitty knockoff” comment once he arrives at the airport, read as very odd, since… he’s back to playing d&d. he’s a nerd. he's proud to be a freak, doesn't care to be popular. so what is he hiding now, the second he arrives in california, if it's not the fear of growing up anymore?
well, number one, it’s important to acknowledge that he WAS still trying to conform in his hellfire era — trying to conform to eddie’s idea of nonconformity, trying to impress him, trying to fit in with hellfire. and he was again, like in s3, abandoning his morals, his loyalty to the party, to lucas, for this. he only starts to find his true self, the heart of the party, again because of will and the painting.
and number two, he's very insecure around el in a way he isn't with anyone he feels truly seen and valued by (similarly to how he admires eddie but isn’t his authentic self around him), so he's trying to be what she wants him to be so she doesn't see him for who he is and not like what she sees. additionally, like i said in the linked conformity post above, there's an interpretation that leads us back to s4 gay mike... but i'm not talking about that right now. either way, things aren't going great for mileven.
after will moves, mike doesn't call much. now, in lucas on the line it's suggested he is depressed and self-isolating. in the show, however, we don't actually... know why he didn't call. we can guess, though, that it was depression, since he seems to clearly be depressed throughout the series, and losing will to california hit him hard (as seen by his reaction to the move being paralleled to will's "death". they've been attached at the hip since kindergarten. now he's a billion years away, and it's intended to be forever, except for some trips to visit. so yes, it's that serious).
so, mike didn't reach out much. called a couple times. will felt like he was losing mike, so he pulled away as well — "maybe you should have reached out more", mike said (in fact, the original script suggested will didn’t reach out at ALL). sure, the joyce was taking up the phone line, but in addition to that... will confirms in the van scene that he was pushing mike away or being mean to him to rip off the bandaid. so he's probably not calling much either, anymore, which is fair. he starts making the painting likely as an outlet for his feelings (and maybe as an olive branch, to try and salvage their friendship. possibly hoping there's an explanation for all this.)
now, mike had pulled away, but then he found out from el in a letter on some random day (likely in january, which has crazy implications — he was rereading, right before his trip, the one letter mentioning will’s crush?) that apparently will might like some girl enough to make a painting for her (which makes his obliviousness in the van scene a little confusing, as finn pointed out, but whatever), and this had NEVER happened before (“it’s not my fault you don’t like girls!”), and will didn’t tell him anything. "we used to be best friends" indeed! this is a big change! so mike starts calling like crazy, trying to fix his screw-up, and can't get through. but then he finds out about joyce's telemarketer job (el mentioned in the will-painting letter that joyce had a new job, but didn't say what it was — surely mike casually asks in a subsequent letter, not expecting it to be the answer to the silence) and "won't stop whining about it" to the rest of the party.
mike was VERY interested in this painting — the script states he was about to interrogate will further at the airport before they were interrupted — and even if it's not jealousy for queer reasons... he’s probably feeling hurt. obviously, we know who the painting is really for, but from mike's perspective, will's got a crush on some mystery girl and he's brought her gift here! yes, mike blames himself, but he's also a weird little defensive possessive creature, so him being jealous and upset and pushy about getting answers... makes sense. especially since he's mr "binder of will's drawings under my bed". he loves will's art, hangs it on the walls, and probably is jealous that some girl is getting all this work from will now. (especially when will's never given mike a painting before, and now this girl gets one?) and! he's also feeling guilty because he thinks he lost will’s trust by saying that thing he said in the rain (he didn’t mean will was gay, just that he’s not growing up like he’s supposed to, but clearly it was taken the wrong way... and he knows it was still bad enough even when read as he intended it) and that’s why will didn’t mention it. like he said, mike feels like he lost will, and blames himself.
it's definitely not suggested he thought the painting was for him until will gives it — in fact, his surprise and delight at receiving it suggest otherwise. why did he let will turn away and cry alone? well, for one, will was clearly trying to hide it, so mike likely thought it was the polite thing to do to pretend he didn’t notice — he most likely wouldn’t want to be called out in a vulnerable moment like that. and two, it's awkward, and confusing, and he probably just did not know what to do, especially since he's confirmed to not know will was lying or had feelings for him, so he... literally has no idea why will is crying? maybe he has some theories, but generally it's a confusing scene for him. plus he's clearly having a lot of thoughts (and looks disappointed/taken out of the moment by the mention of el, and brought back to the turmoil of everything between them), so he's likely doing his usual thing of just pretending everything is fine while he retreats because he can't deal with everything (confirmed coping mechanism btw)
anyway. after this confusing, upsetting, paralyzing six months, of course mike didn't say, during an argument, "oh btw i called you all the time but the line was busy". because then he'd have to explain the time before joyce got the job, and... whether it was for gay reasons or depression reasons, he really can't. the latter being because... he's likely ashamed. he missed will a lot. we know this. but in the end he does tell will hawkins isn't the same without him. so he says it, really. and of course he was awkward hugging will, even if he weren't freaking out after half a year of knowing he was in love with him — he's worried he's ruined their friendship, and is having Many Feelings about that damn painting.
but i firmly believe he was. in love with him, i mean. i truly believe byler was planned, because of the byler writers who left or were shut down/left out of the writing process by the end, the set design and costumes and actors whose behaviour suggests they believed it was endgame, the hints and plotlines and arcs that were suddenly dropped right before the end, leaving it riddled with flaws that byler would have fixed — but all of this goes hand in hand with that. mike is complex and in constant turmoil and him having a LOT of different feelings abt the same issues makes sense. people can feel a certain way about things for many reasons all at once. to me, mike is canonically gay in the way will was canonically gay in s3. like, some people will always think you're crazy no matter how obvious it is. sometimes you just need to sigh and say #ibelieve
