MWC has two networks and less priority and released theirs on Dec 10th.The Big Ten is also in a much stronger position with their networks and has more teams that draw numbers.
The Networks are happy with any Ohio State, Michigan, Oregon, Penn State, USC game with a mid level (Washington, Nebraska, Michigan State, UCLA, Wisconsin, Iowa) and there are plenty of those to go around. The Big 12 doesn't have that luxury and it gets worse if Prime leaves.