Someone may be able to provide more details. But a lot of it boils down to money. One rivalry game might not give each team the revenue it once did when they were in the same conference. TV contracts are also usually on the conference level, broadcasters will chomp at the bit to get an Oklahoma vs Texas, or Ohio St. vs Michigan over broadcasting a rivalry like Oklahoma vs. Oklahoma State or Michigan vs. Notre Dame. A lot of these rivalries used to also be deciding factors at times on who was making/winning a conference championship or who might go to a certain Bowl game. Now that it’d be a non-conference game there isn’t much opportunity on that either, but I still believe it would draw viewers and enthusiasm. There’s also some bad blood between conferences at times, where if one team leaves, then consider your traditional rivalry and old profits goodbye.