How garmadon had an exuse for leaving lloyd and misako had not?!?
garmadon didn't have a choice to leave lloyd initially. he was banished to the underworld and trapped there for YEARS. he didn't WANT to leave his family but the devourer's venom had clouded his judgement. over the years, he began to believe the only way to truly be with his family again and STAY was to become able to use the golden weapons like his father had.
misako, on the other hand, willingly left lloyd at the worst possible boarding school despite having other family she could've left him with. lloyd canonically has at least one cousin on his mother's side, AND early on in the series' run either the hagemans or tommy andreasen explained that the day lloyd was expelled, he'd been given a package of candy from his grandma. meaning that possibly misako's mother was still alive at this point because we don't know if the fsm had a wife or not.
even leaving him with wu would've been a better option in zane's opinion because he didn't know about morro yet.
garmadon fell to the underworld, and later escaped to the realm of madness believing lloyd was still with his mother. as far as we're aware, he did not know wu was not involved in lloyd's upbringing until wu found him in the realm of madness.
how would he? it's not like garmadon had much contact to the living world while banished.
remember, this is from zane's perspective. unlike garmadon, lloyd didn't even know what his mother LOOKED like until we meet misako in season 2 despite garmadon being gone from his life longer.
misako never even WROTE to lloyd while at darkley's, either, as far as the show's concerned. if she had kept contact with her son, maybe zane would've had a higher opinion of her actions.
whereas garmadon proved to zane that lloyd was even more important to him than even his own goal of stealing the golden weapons. he only did so, running off with the weapons, after he knew lloyd was safe.
misako seemed to care more about her research. she even jumped back into the fray to grab it instead of escaping with everyone else. sure, it WAS important, but she JUST reunited with her son and she went chasing after what was basically a duffle bag of dusty scrolls.
i really don't think her and wu jumping out a FUCKING WINDOW together to escape the stone warriors FULLY BELIEVING THEY'D DIE did misako any favors in zane's opinion.
you did hear that little "what?" from wu when they landed on the deck of the bounty?
ok i'm probably going on a tangent here but
WU WAS FULLY EXPECTING TO DIE WITH MISAKO IN THAT SCENE
so, in zane's perspective, misako was going to end up leaving lloyd PERMANENTLY while taking wu with her
zane fucking HATED her for YEARS
because not only did she outright abandon her son, SHE NEARLY GOT ZANE'S REPLACEMENT FATHER FIGURE KILLED OVER HER STUPID SCROLLS
because for some reason this woman had enough power over BOTH sons of the first spinjitzu master for wu to inevitably choose HER over staying with his students who need him.
yeah, zane's mad at her for leaving lloyd and believes that he forgave her too easily. garmadon at least had a BELIEVABLE excuse to leave and later took the opportunity to prove he truly loved his son.
misako, from zane's experience, did not have or do either of these things.
so yeah it's partly zane believing misako is a bad mother but it's also partly jealousy because it was basically PROVEN to zane that misako is more important to wu than his kids
REMEMBER, zane is maybe 14-15 here programming wise when this happened. his dad died when he was 12. he might be the calm, rational, smart one but everyone tends to forget the ninja are TEENAGERS WITH ABANDONMENT ISSUES and zane is probably the biggest example of this.