What other options does BYU have? It's B12, Indy, MWC, or American (new BE).
You take the best available. If the Big 12 crumbles, you go Indy.
If the Big 12 crumbles and ESPN says NO to a contract, you go MWC or American or Indy with BYUtv and some other TV partner.
Or, if the Big 12 crumbles you could pick up the "scraps" like Iowa St, KSU, KU, etc and build a new conference, or go MWC, or American, or Indy...
It's not like BYU was going to stop playing sports if the Big 12 crumbled.