My take on what happened, was that Snyder hit a wall. It happens, and after 17 years, shouldn't have been too surprising. From hiring the right assistants to recruiting, game planning and relating to players, you must be able to balance those dynamics. All the top-notch coaches Snyder had employed through the years, the final two seasons had a drop in coaching talent. This filtered down to recruiting (how much turnover was there in this position toward the end), game planning and training the players. As hands on Snyder was, he still must delegate. Even if he wouldn't admit it, if there's even the slightest lack of trust that your assistants can't manage their responsibilities, you have to make a change. It was speculated (maybe reported) that Snyder wasn't prepared to make such changes, and instead, chose to bow out of the game.
R.J.