The reality is that Fickell is a hot commodity now, but as a G5 team, you have cycles of success/weakness as players come in and out of the program.
He's not going to the Big 12 for at least another two years. With player turnover, there's no guarantee Cincy is still a top team at that point. Plus, while exciting, they're going to have a lot of change in building up infrastructure over the next decade. And that's with the Big 12 almost certainly getting less money/school than the PAC12, and Cincy not getting a full share of it.
It'll be 2025 at the earliest before they get a full share of Big 12 money (same for BYU by the way). 4 years in a coaching career is an eternity.