Jim Delaney and Mike Slive were able to manage the egos in their respective conferences, and get the bigger name members to support and lift the lower members. As you said, both the B1G and SEC acted as rising tides that lifted all of their member schools.
Texas (and to a lesser extent OU) wanted to be selfish, and that only served to destabilize the Big 12. Their selfishness ran off Nebraska and A&M which put the conference behind the eight ball. Colorado and Mizzou recognized the instability and jumped ship instead of riding it out.
If instead, the 2010 Big 12 members had pooled their tier 3 rights, and the LHN is instead the Big 12 Network, the original Big 12 likely stays in tact. That means there are 4 marquee members to bolster the value of the league, and this version of the Big 12 is likely on similar footing to the 12 member SEC and 11 (or 12, or 13) member Big 10.