I watch baseball, and I have seen something similar there, on occasion.
Guy will be burning up Triple-A; but, when he gets to the bigs, he discovers that the guys up there throw pitches other than fast balls. There is a period of adjustment. Some make it, some don't. So,being a big deal in college does not always translate when playing in a professional league.
Exactly. Any of the major pro sports leagues are the “beyond All-Stars” relative to the levels of competition below. Loads and loads of very “promising” talents wash out when they reach the highest leagues. It takes a huge step up from wherever one played before. Some can keep improving and make the transition, mental and physical. Many can’t for whatever reasons.