BYU can play good football and fit in with the B12, but they're not close geographically. TCU was all of those for the B12. (But, really I think BYU could've joined but they screwed up, IMO.)
BYU can play good football and is close geographically to the P12, but they're not a good fit. Even Trevor Matich, who knows more than many on here, said on BYUSN that he could not really see the P12 ever including BYU. He said BYU doesn't fit in. I take that to mean that the P12 isn't fond of BYU for being an LDS-owned institution.