On the conspiratorial level, it’s all political. ‘Installing’ bureaucrats with ideologies.
On the more practical level, it’s psychology/sociology. There is an arrogance that I’m sure (but I don’t know personally) comes with serving in these positions where you believe that because you are privy to the inside information, you know better than the pesky critics who question your every move.
I suspect bother are true, to varying degrees, depending on who it is you are looking at.
Some professions draw different types of people. The type of person attracted to a bureaucracy is likely a liberal, for what reason I don’t know.