It had nothing to do with overall talent, or play calling, or any of that garbage. Urban was too chicken or too stupid to play their best QB from Day 1. Anyone with a brain could see that Cardale Jones was not consistent enough to run that offense with the same efficiency that JT Barett did, plus the ensuing media circus about the QB controversy/competition had to be distracting for the team.
With all that being said, they still likely repeat as MNC (or at least play Bama for the title) if Zeke Elliott had gotten the ball more in the MSU game (and don't blame that all on the OC, Urban is the freaking head coach and could certainly have interfered with the playcalling at some point had he really wanted to).
Although I did read the other day that Elliott supposedly had some type of leg injury that week and could barely walk on the Monday before the game. But still, the ridiculous QB crap almost cost them a couple of more games (eked out a win against Northern Illinois, definitely should have lost to Indiana).
And blaming it on "QB coaching" is just absurd. Whenever Cardale is in the game, they look like crap, and when JT comes it they look just like the NC team did. Yeah, that sure is some crappy QB coaching there.