Still, there are way more hexbear users than there ever were on grad even post reddit migration and many are just as if not more aggressive than genzedong posters especially when federation first began and hexbear still didnt get defederated so I dont quite understand why still.

Because it's not the same as suddenly introducing a radical change to the way your community behaves as a whole. Even though the instances somewhat had their own cultures, the federation was really tight-knit at the time and the overarching feel was more or less not combatative in any way shape or form (with obvious exceptions for new users who are about to be banned for the shit they're spewing). When one user joins and they start a lot of arguments with genuine anger, it's really easy to not engage if that's how your community already is. That person will assimilate or figure out that they don't belong. But when they join with an assortment of others to back them up each confrontation, it's harder to keep the same coherence.