That's Occam's Razor. There are all these complex theories that people in positions of power who come across as idiots must in actual fact be master manipulative geniuses given they can so convincingly fake blithering idiocy and they can't possibly have got to where they are by being so clueless. But the simpler solution is that they are just idiots. Remember also that Eton has a reputation for drumming into boys on a daily basis that they are born to be future leaders and have to be confident of their superiority irrespective of competence or abilities. BTW, has anyone seen Being There?

Edit: Maybe we need a corollary to Hanlon's razor - "Never attribute to genius that which is adequately explained by stupidity."