It's my understanding he was leaving as it was. How long that's been in place I don't know but I first heard of it the first week of December (as I recall, may have been the second week.)Brent Key played at Georgia Tech and he was also roommates at UCF with the new Georgia Tech defensive coordinator when they were both coaching down there. So there were several good reasons why he decided to leave other than he just didn't want to work for Saban anymore. I am certainly no insider but I know Andrew Thacker's (new GT DC) dad and sister. Just trying to shed some light on the situation.
In a sense it's comparable to Tee Martin taking the job at UT. He was looked at by a few SEC programs; Alabama and Auburn being two of them. But, he chose to "go home."