BYU went from a conference in which the bottom dwellers were much better than those in the WCC. Corresponding with that move, BYU's record against the bottom dwellers worsened considerably. That is, BYU was much better against the MWC bottom dwellers than the WCC bottoms dwellers.

IMO, there can be only two interpretations here. Either the MWC isn't actually stronger at the bottom than the WCC or BYU has actually gotten worse at playing poor teams.

I think it's mostly the latter and I don't think we can blame anything external to the program for that problem.