I assumed you meant Missouri. Yes, they were a player most years in the Big 8. Of course we have to go way back into the 60' 70's and 80's. I seem to remember the pecking order as Oklahoma/Nebraska, Colorado/Missouri, and the other four.
The thing about Missouri to me is that they were kind of the glue holding the Big 8 together. Colorado was a little more isolated out west, while Missouri is touching 7 states and these are states with programs relevant both to the Big 12 and the SEC. Colorado was interesting in that they were a bridge to the west coast but I just felt like Missouri was part of what was keeping it from being a completely Texas dominated conference. Now if you look at the Big 12 states, it's a mess and a network doesn't even seem viable with just one big state and small states. There's no doubt though that losing those two states was a big blow in terms of a network or the like. Now, the mere notion that they might get back into Colorado via CSU is laughable. That would be like losing Alabama and getting back into the state via Troy.
Back to the original topic, CSU to the big 12 makes a whole lot of sense market wise.
We are getting into the whole TV deal/market rights thing vs. total population and network deals. Ratings in big markets drove the TV deals but total population and subscriber models drives the network deals. I have no idea how the Big 12 would justify additions though.
Personally I'd rate CSU lower simply because they are not a high profile program, I'd almost think they are more important as a way to gain subscribers in a state of 5 million than anything else. If a network deal was in their future, Cincinnati and UCF would be strong candidates, but can they gain any leverage in those large states with lower tier programs? That's one reason I think BYU holds some appeal, yes it's not a big state but they are clearly a high profile program. I do not like CSU and Houston, I just don't feel like the support structure is there, but I can see the logic to Memphis (population of 6 million, strong basketball program and willing to basically sponsor the conference via FedEx), Cincinnati (population of 11 million, reasonably high profile), UCF (huge state), and BYU (arguably the highest profile program of the bunch, football attendance is 30th overall).
To give some context here's the numbers for their athletic department's revenue:
Cincinnati AAC $52,536,185
Central Florida AAC $51,455,603
Houston AAC $44,815,210
Memphis AAC $43,430,404
Colorado State Mt. West $38,451,203
BYU is private so not on that list but I suspect their revenue would be the highest. It's easy enough to see why the conference doesn't want to share, none of those programs are bringing in a ton of revenue. It would need to be about doing something more than just adding them like they did with TCU and West Virginia with no greater purpose in mind.
For my own amusement, here are some other numbers:
Texas A&M SEC $192,608,876 (fund raising involved)
Florida State ACC $120,822,522
Louisville ACC $104,325,207 (their basketball program brings in a ton of revenue)
Nebraska Big Ten $102,157,399
Missouri SEC $91,217,778 (their population of 6 million produces a nice subscriber base but they have to share)
West Virginia Big 12 $90,523,565 (worth noting that West Virginia's population is small but they support their football program well)
Clemson ACC $83,534,371
Colorado Pac-12 $67,852,236
Obviously the conference deals impact the revenue we are seeing a bit. It's easy to see why they added West Virginia (TCU is private, not listed, but would lower on this list anyway), but when it comes time to talk network or the like West Virginia just isn't worth much. That's where Missouri with three times the population really pulls ahead. Colorado still looks like the least painful loss. But, clearly these new potential additions are not on the same level as what they lost.