If you ever figure out the answer to your first question, please PM me the answer. I assume part of the problem is the intense scrutiny of every last aspect of your life...ever...is something you have to be prepared to deal with. Between the media and opposition research, there will be a record of every time you blew your nose, and it will be on page 1, or in the next attack ad from your opponent. It's insane. That's not an easy ask, and the "best and brightest" probably don't want to deal with it. Howard Stern warned Trump that he was going to fuck up his life forever if he got elected, and I'd say Stern was absolutely right. Trump could have gone on for eternity being the douchebag he was/is, and the average Joe wouldn't have a clue. Now the world...including a lot of law enforcement...knows all too well what he is.

Almost no one voting in primaries is another factor, I'm sure. When only the wingnuts show up, wingnuts get nominated, and one of them wins the seat.