Dabo is a legend right where he is. Not that he necessarily cares about that, but there's no need to go elsewhere and try to live in someone's shadow when you've built something big right where you are. And going back to your alma mater isn't necessarily the best thing in light of that.
In a similar vein, I think Coach Richt should have stayed out of football a year or two, or done something else, rather than go back to his alma mater. He wasn't a 'legendary' coach, but a solid coach nonetheless with a long and steady tenure as HC at one school. I think the Miami job was a complete mismatch for him coaching-wise and personality-wise. He might have done better at a place like Nebraska. O'Leary made a similar mistake trying to chase his dream at Notre Dame. (Assuming he ran a clean program), he could have retired at the Flats like CPJ and been a Tech legend, rather than a successful footnote. Also less pressure to win big at Tech than Notre Dame.