re: SMU singlehandedly destroyed the SWC. What could destroy the SEC?

Alabama, Florida, LSU and Georgia demand, and receive, more of the pie in football. The SEC goes to an unbalanced payout formula in football, creating animosity within the conference. This leads to Alabama starting to call the shots in the SEC a la Texas in the BIG XII.

This leads KY to demand a similar arrangement in basketball.

Dissatisfied teams start looking at other conferences.