I'm really surprised no one has talked about his injury.
It seems obvious to me that his injury changed the calculus for him here.
1. He may have expected early playing time at UT, but now he's likely red-shirting so where he goes is not as big of a factor.
2. The staff at OU can probably at least check on his recovery after surgery if he keeps paying to visit the campus. It's expensive and takes a long time to visit UT, just to have them occasionally check on his recovery.
3. The staff at OU probably knows local specialists in the area that they can refer him to and work with on a semi-regular basis.
All of this adds up to, OU is a better fit for him now.