The domino effect of power-team consolidation always hits the lower conferences hardest. In 2005, it wasn't the Big East that was hurt the most by Virginia Tech, Miami, and BC's departure, it was C-USA that got demolished when they lost Louisville, Cincinnati, USF, and ultimately TCU. In 2012, it wasn't the Big 12 that got hit the worst when they lost teams to the Big 10, SEC, and Pac-12, it was the Big East finally losing P5 status, the remainder of CUSA getting shelled, MWC losing their three marquee teams, the WAC folding, etc.
Same thing was always going to happen here. Big 12 isn't as good as it was with Texas and Oklahoma, but they're not dead the way CUSA and The American are.