And then they run for office..

Or they were raised with terrible and predatory culture. Screwing other people to get ahead is something that is frequently taught in childhood by parents and older role models that were also taught that mentality. We've all seen the Mafia movies and shows, these are family organizations where everyone's Aunts, Cousins, etc. is somehow "connected". There's a big uphill battle for a kid to come up in that environment and turn out like a model citizen. No excuses...