They had relied too much on the run and Avery wasn't prepared to pass to open up the run. They relied to much on establishing the run and then passing. BYU came out daring Avery to pass it but they refused to change their game plan until BYU put up 31 points.
They then tried to pass but he wasn't prepared for it and couldn't handle the zone blitzes which is why even the DE had a pick dropping back.