So, when BYU beats teams like Miami, Oklahoma, Texas, Texas A&M, Penn State, etc. it's because we have better athletes?
Better athletes don't always win. Superior execution and sound fundamentals often beats much better athletes. You see it every week in college football. And, yes, it is the coach's job to teach those fundamentals. And then it is the player's job to execute them.
Our coaches have a solid track record of teaching, as shown by the performance in past years. It's reasonable to conclude that when there is a sudden dropoff in performance, and the teaching is (presumably) the same, then something about the execution is different.