This is just speculation, but I have felt for a while, that those last two years at Florida, that Urban just couldn't look himself in the mirror in the mornings. Before I get downvoted into oblivion let me explain.
There seems to be a prevalent theme going on in northern Florida (UF and FSU) as far as athletes and their accountability in the legal system. At FSU, as we have seen over the last two years, the local police force runs interference for players. At UF, it seems to be the DA's office which gives them a pass. If you compare the number of arrests during Urban's tenure, with the number of cases that actually resulted in significant legal penalty for the player involved, the number drops significantly. Whether it was the legal wizardry of athletic department attorney Huntley Johnson (I joke. He only seems like he must be on retainer with the athletic department) or the disinterest of the DA's office in prosecuting UF football players, cases seemed to drop off. I think one of the final straws for Urban was the aggravated stalking case for Chris Rainey in which he stood outside of the home of a former girlfriend and texted her "Time to die Bitch." Being the father of two college age daughters that had to hit Urban deep. And when the girlfriend refused to press charges after her name was printed in the school newspaper, I am sure he had to have second thoughts about Gainesville. He wound up suspending Rainey, but I really think his heart was not in the job after that point.
I do think that he and his family are much happier where they are now.