It is a mystery!
Aviation seems, so often, simply to use 'past it' pilots as managers. It is as if a big store, say, would let the guy running the elevator advance to running the store after 20 years on the job. Well of course he would have to give the Boss a big 'Hello!' every morning for 20 years as if he meant it. Too, all the little people would naively think that one of 'them' would be such a lucky catch as Manager, when instead he mutates into a self-centered bastard overnight! How can that be?
One of these days I hope to find out. I could have all my 'friends' in one after the other to whine and grovel before my desk and then be sent away empty-handed. Yes, life should then be pretty good, not having to act like some sort of nice guy (a/k/a LOSER) all the time.
Not everyone who gets a smidgeon of power acts that way, just 99% of them. I should be an exception?
As someone once pointed out to me: It is not so that everyone in aviation is an S.O.B. but all the S.O.B.s seem to be in aviation!