sports, means your conference has to stretch from coast to coast --which dooms the ACC and Pac-12-- what is the pathway for both the SEC and Big XII? And is it safe to assume that if the Big 12 absorbed the four corner schools, that the SEC's westward expansion would come to a halt?
It doesn't need to stretch coast to coast. It just needs to have the most valuable brands and markets. USC and UCLA would've jumped to the SEC if they had gotten an invite. SEC, unlike the Big 10, is not bound by this archaic idea that academics of an institution having anything to do with the absolute derth of academic achievement amongst the average NCAA football player. The average starter for UNC is as dumb as the average starter for Alabama. But I digress. The SEC not having an academic restriction made it so they didn't need to reach across the country, but could take a better fit and more profitable set of teams in OU and Texas than USC or UCLA.
The reason the Big 12 needs to expand coast to coast is not because that is profitable, but rather because geography requires it to survive. With Oregon and Washington likely being Big 10 targets in the future along with UNC, FSU, Clemson, and possibly UVA being SEC and Big 10 targets as well, it leaves the ACC and PAC12 with middling to doormat programs. The best of those middling programs will have only 2 viable options.
First is to stay in their current conference provided that the current conference can poach the best of the Big 12 as G5 really has no decent options remaining. Which would see the PAC 12 siphon off the Big 12's western flank and the ACC siphon off the Big 12 eastern flank and essentially put the Big 12 into the group of 5.
Second option is to join the Big 12 to be part of their middling programs. The way to make this option the clearly more viable and preferable is if the Big 12 poached the best it can get from the PAC 12 now and then grabs what the ACC has left after the inevitable defections as mentioned above. Then the Big 12 with the best of what was left after the Big 10 and SEC raids in the middle and west of the country looks preferable to middling eastern teams with G5 dead weight added to already dead weight GT, WF, and BC.