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That is it. No matter what people say if you put up enough money most (not all) would come.
I think the biggest obstacle to overcome is the expectation of success. It's always hard to find someone willing to follow a legend.
I don't disagree with your premise in principle. For instance, I don't envy the guy who takes the Bama job after Saban retires. Even Dabo would feel pressure given the recent accomplishments. I don't feel this applies to UT if you're referring to Fulmer and the years after. Fulmer didn't leave; he was fired. We can argue about how that went down but I don't see that as beneficial. UT's issue was very weak (almost non-existent) oversight of the football program by the AD and administration. It unfortunately has continued well past Fulmer's termination. This athletic program (all sports) is as weak as I've ever seen it, especially men's sports.
I was specifically referencing the last few seasons. Let's face it, the Fulmer years weren't anything special. Beat UF once or twice, managed to squeak our way into a national championship victory against FSU's 3rd string QB, then all downhill from there. CBJ has been a success in rebuilding this program to the level we're at, and I'm not sure there will be too many coaches wanting to step into a situation where the last guy got fired for rebuilding the program.
The biggest obstacle is presuming that with enough money, you could hire a SURE success. So many of the names I hear mentioned are POSSIBLE successes, but there are very very very few coaches who are SURE fire winners, and even they might not be in going from one school/conference to another. Success at the top is not easy to replicate. Think that Mark Zuckerberg could recreate facebook today, no matter how much money he threw at it?