The A.D. that fired him... was it the same one that hired him?
If yes:
I could see that he fired him right away to save his own job. Sounds like a similar Theory that some have brought up about Shawn Eichorst's firing.
I do not know whether the ad was receiving any pressure or if he was disliked the way Eichorst was, but if there were some rumblings towards the AD then who knows, he might have been trying to save his own job.
If no:
I am not sure how much of a possibility there could be for the AD trying to save his own job unless he was receiving pressure as well.