It's all about TV. Texas and OU are pissed at the TV deal, and watching other teams scoop up the money and TV audience.
UT and OU have sweetheart TV deals in the B12. Their TV income is on par with the B1G an SEC. Obviously, if they were to bolt to the SEC, the package for that conference would increase pretty dramatically and their payouts would increase. But, this is more about the big revenue makers in that conference looking out for themselves.
Money for sure is the driving force, but it goes beyond the TV deal for conferences. Look at expanded playoff implications and the seemingly inevitable march towards super conferences. It's a consolidation of power and money in the hands of the biggest schools and not terribly different from the European Super League idea that was attempted this year by the biggest clubs in european football.