Missouri has a long tradition in the B12. More precisely the Big 8 before they fell for the Texas Merger with Texas, texas Tech, A&M and Baylor.
The Kansas/Missouri rivalries aren't kissed off lightly. If UConn and BC had 100 years of football rivalries it would be similar. 1907!
Then there's the hard reality -- Texas tried to throw them under the bus in 2010 and again in 2011. Big 8 conference mates Nebraska and Colorado knew enough to leave. A&M knew enough to leave. The 4 predators are still there. Waiting for a better deal to gut the remaining members of the Big 8.
They have to go if the SEC beckons. They want another 100 years of tradition and rivalries and yes, a stable income flow.
If by "fell for," you mean "joined forces with one of the largest markets and pools of high school talent before their union of worthless Plains states was unable to get a competitive TV deal," you're spot on.
And actually, Mizzou actively courting the Big 10 (and CU the PAC) over the last several years set off the almost conference armageddon of 2010. Nebraska always had its panties in a wad because Texas refused to join the Big XII until Nebraska discontinued its tradition of using state scholarship programs to inflate their roster and admitting partial qualifers...and then repeatedly beat them on the field. God forbid there be actual academic standards.
What meaningful tradition and rivalries is Mizzou going to have in the SEC exactly? Kansas and Missouri are border states with a lot of shared history that has nothing to do with football. In fact, the football has been mostly terrible.
A&M leaving was just stupid. They're joining a conference where every big program has its own Tier 3 rights, is dirty as hell (as in dealing with street agents, paying players, and a bunch of other stuff Texas doesn't do), and will out-recruit them in their own respective backyards and possibly A&M's. What's especially funny is that Texas approached A&M with a joint network proposal years ago. A&M was too rudderless and visionless to see the potential, and now they're using the LHN as an excuse for doing something their own president admitted they were looking to do months before the LHN deal was even inked.