First, we will never really know. If he ends up winning championships and medaling many times then it was not the wrong choice. It looks like he is going to go to college (just as Allyson Felix did) so he can get an education. Considering he was not going to Stanford or Duke anyway that is really a non-starter. Of course he might have ended up with the exact same career had he gone to college.
If he does not succeed then there is no way to say he would have succeeded had he gone to college. Look at the number of distance runners who go to college with a great resume coming out of high school and do not progress very much. Isn't one of the knocks of running in college is the long season and college coaches not looking long-term (not that that applies to all coaches)?
The key is there are many ways to reach the top and we are not privy to the contract or his family situation (although I do not get the impression financial pressures play a role here). If adidas is paying for his college (not uncommon in such contracts it seems) and he is getting a paycheck then it seems like a reasonable move to make.
As I have written in other places, changes to NIL could mean kids like Kessler don't have to make such a choice in the future. Of course it might mean shoe companies have more influence over where a kid goes.