Joining the sec should have made them rich. I have no clue why their finances are in such disarray, but their revenue has definitely done up from the conference payouts.
Made them "rich"? No way.
Football wise, they are not getting good Texas HS recruits anymore, and attendance wise fans do not come to see South Carolina, Vanderbilt, Florida, they liked Oklahoma, Texas, Kansas, K State, their regional foes for decades.
Yes the SEC revenue was better but Missori athletics are slowly going downhill each year since they joined the SEC, that extra SEC money will not matter.
The University itself is in organizational and financial disarray, have made terrible choices at the highest of levels, a few years ago yielded to outside antagonists when the football team threatened to boycott vs BYU late in the season... long story. Bottom line, they are in a death spiral.