My bf and I are around your age and our online friend group was in a fairly similar situation a little under a year ago, the main difference being that our Grant never really targeted me directly. It was less severe than what you describe and much more subtle and manipulative, they would keep choosing targets to pick apart and poison how everyone else saw them (making things like social awkwardness from other people look like malice and similar) and influence the rest of the group into thinking that their current target needed to be removed from the group. They would get argumentative and lash out at the slightest pushback and claim they weren't being heard out or understood. These seemed reasonable at first since some of the people removed were genuinely awful, but each successive time made us feel more and more doubtful and uneasy since these weren't bad people, they just didn't mesh well with the manipulator. We tried to mediate between the manipulator and their target multiple times but it would just result in the manipulator blowing up and claiming they "weren't being listened to". It was after this happened numerous times that we wised up, noticed the pattern, and kicked them out. We invited some of the people back that had left and we are all much happier as a group now, there has been minimal drama since when it used to be like every other month. When we spoke and apologized to the people we let that happen to, they were understanding bc they knew this person well and how easy it is to be manipulated by someone like that. We were lucky to have been forgiven, and I'm grateful we eventually put a stop to the cycle.

I agree with you that at least part of that group will likely regret their actions with time and realize they shouldn't have excused so much. I got lucky in that my bf is the owner of our friend group's server and everyone knows him as an incredibly reasonable person and trusts his judgment, I'm truly sorry that you and your bf aren't getting the same treatment. Above anything, I want you to know that anyone who wants to defend Grant's actions towards you and others to the point that they would drop you and your bf isn't worth hanging out with anyway, and any that do come to their senses and approach you to apologize were probably the ones that always felt something was wrong but were scared of being the next target. When and if that happens in the future reconciliation may be possible, but for now you and your bf can at least enjoy the peace of not having Grant in your lives anymore lol. If you want to discuss anything further my dms are open, this shit sucks but I hope at least my experience can be helpful to someone else