Anything under 90/60 is considered low. It isn't always an issue, but it's not surprising they were fainting, having dizzy spells, etc. with BP that low.
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.
Calling hexbear a "trans instance" is pretty misleading. They're explicitly political first and foremost, and happen to have a high concentration of trans/queer users. They were defederated by .world for being overbearing and disruptive, not because of their transness or queerness. Blahaj zone, by comparison, is explicitly a trans instance first and foremost, and is still federated by .world.
I'm gonna stick with weed, but enjoy!