Also think managerial appointments are increasingly becoming a completely random grab-bag in terms of success. Manning at Norwich was a great appointment at the time, and we'd have 100% taken him here, yet he's led them to the worst start in the club's history. Still should have done much better at Southampton - even higher up, there was no reason for Potter to be so bad at West Ham, Andrews is doing much better at Brentford than anyone expects.
So much of the success (or lack thereof) for a manager at a club is unquantifiable 'vibes' that you really can't judge anymore*
*Rooney will always be shit