He coached for the Rams the 3 years prior to his first UK stint. My guess is he was worried about his job, or he thought being the OC at UK again could get him a HC job in college.
Look it's ok to be a Vol fan AND objective. You can't teach speed and that is Hyatt's strong suit. He is not elusive after the catch and rarely breaks tackles. Had several drops in the last few games as well. But he can fly and simply run by dudes and he is a decent route runner. I watched Harrison in a few games and the contested catches he makes are what make him elite and sets him apart. he is very strong and that is important at the next level especially vs press man.