This is not so much a theory as it is a fact. This is probably the most universal answer for why a player had success in college but not the pros. Ask any NFL executive about draft busts, this will in all likelihood be the first answer you get every time. And the answer is simple, not overly complex, the answer is put very simply. Some kids aren’t smart enough.
College schemes, and systems aren’t very complicated, so you never know which player can, and can’t learn an NFL offense or defense. One thing that not many people understand about pro football is the complexity of the sport. The players don’t need to be smart, they need to be brilliant. That might sound strange, because stereotypes tell us that the NFL is made up of a bunch of meat-heads. But when you look at NFL players IQ and Wonderlic scores, they are mind blowing. (The Wonderlic test is a less commonly known test but it is designed to test a persons aptitude of prospective employees for learning and problem-solving in a range of occupations.) So when we see how smart an NFL player actually has to be, it makes more sense as to how many players just cannot grasp NFL schemes, and systems. Because college athletes aren’t asked to learn anything complex, so you never know if the player can handle the NFL schemes. A good hometown example is Wes Welker. By NFL terms, Wes Welker is an extremely underwhelming athlete. running a poor 4.6 40 yard dash, at such a small size, and not being a very strong player. But he has an uncanny knowledge of defenses. He has a keen ability to watch a defense develop on a play and know exactly where to run. What the average fan doesn’t realize is the Brady, and Welker never had a clue what route he was going to run before the play started. It wasn’t until the play developed that the ball was thrown, And it wasn’t random. every single time, Brady knew right where Welker was going, and Welker knew right where to go, because they both read defenses the same way, and went to the same places every single time. So when we look at an example like Wes Welker it makes sense as to why he went undrafted and barely even got a shot in the NFL. Because he has many of the intangibles to play in the NFL, but often many of the intangibles that it takes to have success don’t translate to the NFL