I moved from Lemmy.ml because I liked the name of Lemmy.world and it ran a newer Lemmy version which meant I could make communities. I moved from Lemmy.world because they defederated from piracy communities they didn't even host (but for some reason still kept the small piracy community they DID host) From thelemmy.club because I couldn't see the Hackintosh community from there (probably defederated) Now I spent some time looking on join-lemmy.org and checked out some instances and this (lemy.lol) instance seemed good, so I chose that.
Hexbear was defederated from world for the same reason they defederated from lemmygrad; the admins of world are anticommunists. You can make a very easy argument for banning hexbear for their toxic users, but the same can't be said for lemmygrad who are way chiller.
I seem to remember that given as the official reason, and there were certainly plenty of complaints along those lines. Whether that was a convenient excuse for anti-communist schemes or the actual reason I don't know. Most likely it was some of both, at least in the case of hexbear.