I look at it from a different perspective. Perhaps he was part of molding Mahomes, considering Mahomes was not highly rated in recruiting, and that's how he ended up at Texas Tech. It's not as though TT gets a lot of talent, and other than Mahomes there wasn't much talent at TT during his tenure (I believe Keke Coutee was his top receiver).I wouldn't want Kingsbury. He was barely over .500 at Texas Tech with Pat Mahomes at QB. He was right place right time for the Arizona job. They decided to draft Murray and hired a coach they thought could get the most out of him. His air raid style offense may have been ahead of the curve 10 years ago but not anymore.
I do like that he's on the list though because it does show they are looking out of the box.
As for his time at Arizona, passing game actually wasn't his most impressive improvement for that team. It was the running game, because the year before he took over the Cardinals were dead last in rushing offense with like 1400yds. His first year as head coach they jumped to 8th in the NFL with like 1900, and followed that up the next season by being 7th in rushing with like 2200 rushing yards.
Do I think he's a good head coach? Perhaps not, but I definitely think he can be a great OC.