Very good question, but it happens all the time. I'm a little reluctant to let a 39 year old run the Panthers, but fortunately I don't get a vote.
I think young coaches can be good, but business experience can't replicated without actual business experience. Just my two cents.
In fairness, DeCosta is only two years older.
Most of the other guys are in their late forties with the exception of Gettleman who's over 60.
I guess you have to look at "age" vs "experience".