Let's recap
Riley made the decision. I never said he came in one day and said he was going to fire the man. He did his due diligence and planned it. As most recently mentioned by SE himself, he is not involved in the running of the program. He is engaged on matters of personnel, like in any organization, but he doesn't instruct his direct report to hire or fire someone. He may provide input on what he thinks, but he leaves the decision up to the coach. You are and others are already trying to put the emphasis on the AD telling the coach how to run his program. That is now you successfully manage a large organization. So I'm telling you that Eichorst wasn't blindsided by this, he was kept in the loop as appropriate and he was involved as appropriate, but he isn't meddling in the affairs of the football staff.