gosh i am so so sorry to come into your askbox with this but you seem a knower of things and as an extreme latecomer to this fandom, i have been. a little bit genuinely mystified by the ""dadza"" phenomenon in general? like i've seen figures or characters Assigned Dad At Fanbase before but it's usually because of like. dad hobbies or jokes or fashion sense or an actual child they talk about often or a tendency to actually make "ah yes, i'm your dad" comments/jokes, none of which the real streamer seems to have or do, or a some manner of "gruff character is soft and caring under the surface and looks out for children" archetype, which his RP character doesn't seem to be (outside of MAYBE qsmp, the story that literally became about parenting through peril, but i know this goes back further than that). Is it just because he's older by internet standards and people can't imagine people with more than a 3-year age difference interacting in a way that isn't """parental""? was it a one-off joke that got taken too far? is this all a symptom from the dsmp plot point that snowballed to the extreme? i need to ask because it is just SO far-reaching and i see no clear origin and as you can imagine that is confusing.
Okay so. This is a fascinating question because as I throw my mind back I am a little fuzzy on the actual order of events. I think it was a bunch of things happening that kind of compounded, but to the best of my knowledge what happened was:
Through SMPEarth and MCC, the original sleepy bois becomes popular. Technoblade, Philza, and Wilbur Soot. Shipping is frowned on, so people start getting invested in a family dynamic (often with all three of them as siblings). Through a MCC win, Tommyinnit (also exploding in popularity) gets added to the "official sleepy boys" dynamic, and now we have 4/4— still often interpreted as siblings, if you ever read Snapshots in Lavender, which is drawing from this time period.
Wilbur particularly is huge into the family dynamic, often talking about being twins with techno, brothers with tommy, and referring to Phil as dad and Dadza (cause he was ten years older and that means of course he's OLD and DAD, and Wilbur had a daddy kink). When SBI joins DSMP, wilbur takes the opportunity to canonize Phil as his dad in lore at the same time as he makes Phil kill his character, and tries repeatedly to make Techno his twin, and refers to tommy and him as "like brothers" a lot. Tommy plays into the dadza stuff (he is like a decade and a half younger than Phil so at least it makes more sense) and also is clearly relying on Phil for things like tech support and moral support as the fandom is exploding. Phil is dependable and safe, therefore dad. Fandom takes this and RUNS with it. Passerine happens, and Phil gets written as the dad of wilbur and tommy, Techno as an ambiguously sworn brother to phil, and brother/father/mentor to wilbur and tommy.
Pandemic is happening. 30k people are showing up to Phil streams. TTS off kids basically in distress are latching onto Phil as a supportive and dependable figure who they are seeing as dad in fanfic and on Wilbur streams as Wilbur is playing up the dad thing whenever he interacts with Phil. Phil is like (to the fandom) sure if you haven't got a dad or a good dad you can call me dad I guess and just sort of laughs at his friends calling him dad.
Techno puts his foot down in canon that Wilbur is not his twin, though that doesn't stop either Wilbur or the fandom, and Phil clarifies that Tommy isn't his kid, and Techno isn't his kid, just Wilbur, and this does not stop fandom at all. Tommyinnit's Unbeatable Method and Clinic for Supervillains are written in this period, and Phil dad and techno+wilbur+tommy trio of kids are locked in. Other huge fanfics use this lens— importance of being kind, ars poetica, his curse of binding— a few people such as silverwing are doing techno and phil platonic marriage with wilbur and tommy adopted kids, but the phil=dad lens is inescapable. Even bones in the ocean, which I think might be the biggest phil-centric fic, has a subplot about him being wilbur's dad and how that went.
We start getting into fandom schisms about if Phil is a good dad or a bad dad in canon, with his treatment of Wilbur/Ghostbur/Tommy being variously argued. A common refrain is that cc phil is a great dad, c phil is a terrible dad, so this fic is writing phil as a good dad cause that's what's real. Phil in real life continues to have no actual children, but the fandom refers to Phil as techno+tommy+wilbur's dad so often that he puts "father of three" as his end screen. [EDIT: i have been informed that Tommy made that and send it to Phil and told him to put it as his end screen, so that was still Phil just playing along.] It becomes a common interpretation that okay in LORE phil is only wilbur's dad, but in like pure SBI phil is everybody's dad, and people are writing just the pure character dynamic, not LORE. This is still tagged as not RPF. Dark SBI starts to happen.
The DSMP kind of stutters to a halt, with various endings good bad or contentious. Technoblade passes. The fandom declines, but the fan fiction is kind of self sustaining at this point and has firmly established character interpretations. People are regularly showing up to Phil streams to call him dad. He keeps saying that he's just a guy playing block game, but it's fine if people call him dad if that helps them.
QSMP happens. Wilbur immediately assigns Phil as his dad again, though Phil manages to wiggle out of it enough to say that it's not a bio relationship, they just met on the train. Phil becomes a father of an egg child, and the Phil good/bad dad wars start up again. People start interpreting DSMP canon through the lens of Phil's QSMP actions and explaining how that makes him a good or bad dad. However, shipping is kinda legalized due to Phil having a (platonic) husband, so the lens of viewing Phil as a character in a relationship starts up, but the phil-dad people also continue, notably interpreting team bolas as a family with phil as the dad, and starting wars on the wiki about who gets listed as Phil's family and how/why.
Wilbur is revealed as a domestic abuser, the QSMP ends, and both arms of the fandom decline again. Phil's stream numbers are declining to a more manageable level where he can actually read chat and respond to donos, and he starts responding more firmly to people saying that they love him, dadza, saying that that's parasocial and they don't know him. He is notably no longer laughing at it, and he re-emphasizes that he's just a guy playing block game on the internet. We still get like one dono a stream fully latched onto him as their dad.
A year later, Phil blocks dadza in his chat.
Which is to say to my knowledge it mostly came from fanfiction/other people, and Phil went along with it, and now he is no longer going along with it. He has never seemed particularly dad-y to me, but people viewing him through a wilbur-centric or tommy-centric lens had that wiring laid down for them, and then the fandom fucking Took Off With It with how popular those characters/character focuses were. That's my understanding of what happened, if anyone else wants to chime in go for it.
