The PHB is thinking, "My work here is done."
An idiot in the team can work:
you need a team of N 1 for political reasons, but only have N smart people; your smart meetings bore the idiot, so you never seem them;
it useful to have someone point out the emperor-has-no-clothes, or there is an elephant-in-the-room;
The PHB measure of performance may key in to what an idiot can produce, leaving the smart people to try and solve some real problems.