People typically get stupider in groups.
3 is the magic number. 3 bosses standing around one worker. 3 guys harassing a girl or a guy. 3 everyday girls become MEAN GIRLS when together and harass everybody.
It’s possible to go in the other direction – to have a group of 3 (or more) go UP in quality rather than down but that takes a charismatic leader. Otherwise, its the one that lets us feel we can get away with our worst traits will prevail. That’s my theory anyway.