Is it not possible that there is a correlation between high IQ and better self control? That explanation would fit the facts just as well as Carolyn's without casting shade on massive groups of people for no reason.
It's not fun to be in those positions, but it happens, and having a stomach for that kind of ugliness over the long run is what allows people to work in those kinds of positions. That may select for psychopaths, or for people who can overcome their emotional distaste, which can look superficially like psychopathy I suppose.
http://www.amazon.com/Emotional-Intelligence-Matter-More-Tha...