It could be one of those "The Road Not Taken" things. Play it safe, stay put, and regret what might have been for the rest of your life. Even if his experiences don't match up with his expectations, at least Williams will know what happened.
Williams has been here this long in Nebraska so it might be getting to be a grind. Why not go somewhere else, learn something different, see something new, meet someone else? He's at the time in his life he can and should do it. It always struck me as odd that so many kids in Columbus say that they can't wait to get out of this town to see something new and then go to...UNL...70 miles away...and hang around with the same kids that they knew in Columbus. That really broadens one's horizons, doesn't it?
One last thing: This Hughes firing / mass exodus of the defensive line was one of the bigger stories last year that leaves a lot of questions unanswered as to what happened. I think it tainted relations up past Hughes because Riley didn't fix it fast enough. Not unlike getting mad at the boss of your boss because your boss is an a-hole and his boss doesn't do anything about it. Can't prove it, but have seen it a thousand times, sure looks the same thing here. Some guy looks at where he is and says "I'm not doing more of the same, I've got to get out of here." Then everybody says, Well, why is he leaving, he's been here 20 years, what does he think he'll find somewhere else?" Sometimes it is what one WON'T find at another place that prompts the move.