I see where you are coming from, but Colorado wasn't close to the rest of the conference in many ways than just geography. If only Colorado has left they could have easily been replaced by a school like BYU.
Colorado wasn't the lynch pin of the conference. UT/OU and Nebraska were. Nebraska leaving is what started is what showed the weakness in the Big12, and physically made the conference weaker.
That opened the door for the PAC16, and for A&M to start talking to the SEC.
I think UC's differences cemented the sort of institutional personalities that could exist in that conference. No disagreement about Colorado not being the heart of the conference, but if UC didn't see it being worth their while, almost emphatically, I think it started clearing the way for the rest. You either dealt with the UT/OU political clout, or you didn't. UC wasn't going to anymore...but, they kind of felt that way almost 15 years earlier, too. The others had a bit more tolerance.
When Perlman discussed how Nebraska secured its Big Ten spot, I thought he said the conference knew Colorado was gone, which I took to mean that regardless of a PAC-16 cluster or not, the PAC was going to expand, and that expansion included at least Colorado. Who the other one or five schools were was up to those Big XII institutions. It was Nebraska, Texas, and Missouri who were then the ones targeted for wandering eyes/commitment issues at the summer meetings, and while I agree Nebraska was probably the
catalyst, I think both UNL and UC upgrading together pretty much did it for all. A mover and a minor member both moving up is painful. I don't doubt for a second Missouri got some extra courage institutionally from two of its longtime rivals peeling off. UM wasn't a major player, but they were valued elsewhere by someone better.
I know it's splitting hairs, but I think the kind of "free pass" Colorado got when they announced and left, like it was always on Nebraska, or A&M and Mizzou thereafter; it really wasn't. And I doubt the Big XII could have even found a school that would have properly replaced what Colorado brought to it. BYU would have fractured the footprint, Air Force (assuming they even were to agree) was too small and would have been a punching bag, and others like UNM, CSU, Tulane...didn't budge the needle at all. I don't know if anyone could have made up them academically (other than Rice or Tulane). Nobody filled in all the boxes they checked: big (30K+), AAU, public, sizable state, a school by a top-25 media market. Good luck with that. And, Colorado's one of those states now, kind of like Missouri: undervalued and under-appreciated, but both populous, diverse culturally (and politically), and a gateway state. Losing UC, like losing Missouri, hurt that conference in an almost irreparable way, and I think the understated importance of those two programs is part of that issue. WVU athletically might have balanced the loss of UC...it didn't academically or institutionally. Not even close.
I kind of always thought UC and Washington were similar in certain respects. Boulder's no Seattle (and vice-versa), but when things are good in their respective place, they can be among the most recognizable programs out there. If/when UC "comes back to life," people are going to see just how good of a score the PAC made. And I think the B1G would even be jealous (since they wanted them, too).