I don't know why. He's was a very good and VERY tough kid at Colorado who went to class and had a high GPS. A bit undersized and average throwing arm, he was reported to be the most pro-ready QB in the draft.
Could this slide be because of that ONE bad interaction with Dabol? Bottom line is that he'll eventually get drafted by someone even if its the 3rd or 4th round. Who cares. Once your on a team WHERE you were drafted matters little or nothing. Then it's all about competition and he IS a competitor.
His dad can be a bit of an ass, but he could have rested on his laurels and done a side gig at ESPN or somewhere. Instead he chose to put in the EXTREMELY hard work to go to a HBCU college and hone his craft successfully and do the same at Colorado, reviving THAT moribund program back from the dead.
He has a style that can rub SOME people the wrong way, but you HAVE to respect what he has accomplished both as an athlete AND as a coach.