Colorado was almost in the PAC for the 1996 season. In 1994, CU thought they were going to the PAC with Texas. When Texas decided to go the Big 12 instead, the CU Board of Regents voted 5 to 4 to decline the impending invitation from the PAC and join Texas in the Big 12. A change of one vote would have put CU and Utah in the PAC for 1996.
Good reminder there. Texas wanted to bring other Texas' schools with them wherever they went. So, hooking up north with the old Big Eight became the deal. Outside of the Oklahoma schools, resentment seemed to linger, and integration in attitudes never reached completion. Even the Oklahoma-Nebraska classic got reduced in frequency.
Texas also at the time, was against going to the SEC, while Texas A&M had the desire. But then, Texas and Texas A&M taking seperate avenues had more forces to keep such from happening.
Even after Arkansas left around '90, the Southwest conference still had eight schools, but all were in Texas. The private schools were struggling, and the SMU suspension sanction plus other schools earlier having NCAA probation penalties imposed, the conference had a diminished outlook.
Had those Texas schools stuck together through the difficult period, and actually expanded, so much may look very different today. They could have gone for a few of the now MWC/former WAC schools, and possibly pursued a few from Tulane eastward. There were actually some more eastern choices then that were in negotiations with other conferences.
Then though, the mindset was more contiguous and regional in nature. In any case, I believe Texas and Texas A&M wanted to separate from most of the Texas private schools and would have left for somewhere anyway.
When C-USA came along, and Houston was wanting something better, the whole Southwest Conference dissolved. It was only a few years earlier the SW Conference was a real power, and the Cotton Bowl was among the great ones.
The unclear thing for the MWC, is that the PAC12 and/or the B12 could extract from there at some point as expansion is not settled for the long-term. Also, some of the MWC schools and a some of the AAC schools may try to create a new conference in a effort to gain some inclusion with the power 5. I see some have discussed a bit that thought here. But I don't see that happening right away, because the stronger AAC and MWC schools are all looking for invites from the Power 5.