He was at Michigan State, Alabama, and LSU. You think those schools were ever devoid of talent? His record at MSU was pretty mediocre.
A coach's ability to hold players accountable at a school like Alabama or LSU is much greater than at BYU and it's not even close.
I'm not saying you can't or shouldn't hold players accountable at BYU, but it doesn't even remotely compare to the ability to do that when you're a coach at LSU or Alabama. It's a far greater challenge at BYU for many reasons.