I believe there's something in the water in DC. Seems like every good person who gets to Washington in time either gets involved in some scandal, or loses their backbone in order to play the Inside-the-Beltway-Game. The simple politics of Washington seem to have a corrupting influence on good people.
Every member of congress lives the lifestyle of a millionaire, even if he doesn't become one. Each one is surrounded by a cadre of adoring sycophants. It must be very intoxicating. I believe that at least some go to DC to try to improve things. Few do.