Had a long-time friend group explode last year over this. Years of behind-their-backs shit-stirring lies by a couple members of the group finally got figured out and called out, publicly, which lit the fuse. Exact same behavior that was called out was immediately employed to try to spin that and get these people's "enemies" pushed out of the group, which was the bomb going off. About half the group survived with some scarring, the rest just shattered.

Toxic people gonna toxic.

> There’s always going to be a shot caller or instigator behind it and everyone else who is weak willed will get on board with it.

Yeah, a major factor was lots of people putting up with some real bullshit for years to try to keep the peace. That, and the ones who did try to do something about it approached the problem-people one-on-one, which just led to them being lied to ("oh no, there's no problem between us") and then smeared even harder to others, and marginalized, having no idea why any of it was happening.