He walked away like a man once he realized that he just didn't have it. He could have easily swallowed his pride and fired Jon, but it would have been a hollow gesture. It was time, he gave up millions, but he did the right thing by stepping down.
Even if he tried, ESPN would cut his mic. Too many people's livelihoods depend on the SEC being beyond corrupt for one person to be able to blow the whistle on it.