Because he has been in DC too long. He's been there since 1995. Even the good ones become corrupted by 'inside-the-beltway' mentality ... must be something in the DC water supply.
Can you imagine how strong an individual you must be to go to Washington DC and remain a rational, ethical person? I don't think I could survive without running away. No decent person could, it seems.
And that is a big, big problem.