Big 12 might be a better culture fit, but it's also about geography.

If the Big12 decides to expand, they've got a ton of feasible options (UCF, Cincy, Memphis, Houston and BYU). With W Virginia already in the fold and no teams on Mountain time, it's likely that conference looks east if they expand. Bringing in BYU would give them another outlier school without a travel partner. And you might personally think BYU is still the best option of those expansion candidates despite that. But it's at least debatable.

But the PAC 12 is limited by geography when it comes to expansion. Their top options are BYU, Boise, San Diego State, UNLV, Air Force There's zero doubt that BYU stands way ahead in that group