For political appointees who are implementing your promises that determine whether you get re-elected, loyalty is a very important qualification.
We all know how easy it is for political promises to be broken - there are any number of ways to sabotage an effort you're in charge of, while appearing to act in good faith.
You don't even have to do it deliberately - you just need to give 100% in a job that needs you to give 110%.
Who do you think has more incentive to deliver your vision? A guy who hates you, and who thinks he'll get a better boss (maybe even be boss himself) if you're out of the way? Or a guy whose ship is tied to yours and if you go down, he'll never achieve such heights in his career again?
