Because the PAC 12 had a complete idiot as a leader and the PAC 12 was been nothing but scraps since Pete Carroll left for the Sea Chickens, exact for a one off here and there.
TV pays the bills, this is nothing new. You think the networks run the NFL? They work in partnership with the NFL. Just like the SEC/BIG 12 work in partnership with FOX, ESPN, etc. TV is never going to run CFB, why would they? They will work with their partners to do it. Do you think TV wants CFB down to 20-30 teams? They want to fill content and have as many fans as possible thus drawing the most viewers. They'd rather have 60 teams than 30. With 60, Kansas State, Rutgers, Ark, Ok State, Arizonia, etc., type fans will not only watch their teams, but the big games as well. Cut teams 30-60 out and many of those fans will likely gradually lose interest in CFB.
Sankey and the power brokers in the SEC aren't going to give up power to the networks. Same with the Big 10. They are stronger together. They will work with the networks, but never going to let give up power.