> if he's that bad the people on his team will leave and his behavior will be that much more obvious.

Often not true: while such people don't do great (programming) work, they are very political adept (which also includes being good at bullying outsiders), so often being a "disciple" of them is very useful for your career. So, while many people may not particularly "like" such a person, they often become "disciple" of him for such a self-interest.