Great ass’t coaches
Good ass’t coaches
Poor ass’t coaches with names that get you jobs
Tell me which got the Green Bay job
I think only time will answer your question. If he is a successful head coach, he will be looked on as a successful assistant who rose in the ranks and was worthy of the promotion. If he's not successful as a head coach folks will say he was never cut out to be a head coach and will question whether he just got the job because of connections. Hindsight is always perfect in these kinds of matters.
I'm reminded of my own tangential involvement in the hiring of Cleve Bryant. I was one of the first to suggest to the AD that we had this alumnus who had been a fabulous football player for OHIO, was now a great assistant coach at North Carolina, where he was credited with several recruiting coups, and would be one of the first black head coaches in Division 1 (second or third, if memory serves). I could see no downside to hiring this man as our head football coach. Well, hindsight paints a far different picture. If Cleve had, indeed, been a great head coach and OHIO had won championships with him at the helm (and he hadn't had off-the-field issues), I would have been a coach scouting genius. As it is, I belong in the Hall of Shame for Alumni Stupidity. [Let me ad, that the AD was smart enough to ignore my phone calls and memos and personal discussion and to recommend the hiring to Glenn Mason, only to be overruled by President Ping.)