I know nothing, but trying to take a bit of a different perspective on Urban Retiring.
In my Life time, I've know nothing but OSU firing their head football coach. Urban survived a huge scandal, I doubt he would have survived another one.
I think head coaches can try to instill a cultural of doing things the right way (and I think Urban was doing this,) but there is no way you can keep 150+ people always in check. One more slip up and I think he would have been fired. His retirement may just be him making sure he is leaving on his terms.