There are many players who were absolute studs in HS who never make it at the college level. Just like there are many great players in college who can never catch up to the speed in the NFL.
It is also possible that he does have a hole in his game that is not apparent playing HS opposition - although I doubt this is the case. I am confident that it is an honor code or personality thing. It's also possible that his bishop would not sign his ecclesiastical endorsement for this season.