Coulda, woulda, shoulda. Perhaps it is eating at him, what might have been had he used the head on his shoulders (more than the one down below), stayed at UT and worked at building a new SEC powerhouse where once one existed. Perhaps he has matured some. And might even want another crack at the HC job in Knoxville. But more likely he has just been trolling - trying to take advantage of the notoriety UT has attracted with our poorly managed coaching "search" and subsequently the hope we now have with Pruitt at the helm, to get himself some easy publicity. I will admit, when things were looking grim just before Currie's firing, in a sense of desperation I even posted a couple of pro-Kiffin posts. But just like the Gruden dreams, that genie ain't never going back in the bottle.
EDIT: I don't rule out that he might both be trolling AND actually want to coach the Vols again for whatever perverse and selfish reasons. But to use another metaphor, that ship has sailed...