Nobody seems to know. Apparently he missed two games one year with a foot injury and missed 3 games last year due to a positive COVID test. I don't think that counts as injury prone.
Apparently teams were waiting on some medical information on him that, because there was no Combine this year, didn't get to teams until yesterday or the day before. But whatever it was, the medicals were apparently good and he started to rise up on draft boards. Maybe he just hadn't had the normal physical that players usually get at the Combine so teams had a red flag on him until they saw the result of a physical?