With a stable of NFL caliber backs like Unga, Fui, and Tonga running behind it.
I'm not saying Retzlaff is Max but he made around ten high difficulty precision throws against SIU last week and probably six or seven quality throws this week.
BYU had a tremendous D in 2007 - held PAC opponents plus Utah to an average of 11 PPG in three BYU wins. That's why Max won those games.