Yes. About "evil" groups. In one case, corrupt cops and the other a motorcycle gang. There is plenty of material as to why these groups stayed together for so long. Probably the most relevant is surviving against a greater "evil" force at play.
I don't see evil as the reason why groups fold. I think it's the perceived chaotic aspect. As long as there's a goal, which every campaign should have, there's really no reason to turn inward.
Yeah. It all sounds great and reasonable. And the idea that a group with a goal should have no problem sticking together works great...as several other posters have said. Logically, conceptually, it makes perfect sense.
I simply have not seen that work, in the long term, in actual play with actual people.