Horrible defensive game plan. You could tell that Oregon understood BYU's defensive weakness -> upfront pressure.
If the QB is Nix then you force them to beat you with his arm. Plain and simple. Oregon understood this so they ran it down BYU's throat and BYU would not over commit to the run.
Conversely, Oregon positioned its D to be beat by the run. BYU couldn't run the ball so they lost.