[tdw28210]

Multiple reasons, but often times really good QB's in HS and college can simply rely on their sheer athleticism to excel at those levels. They can get away with misreads and bad decisions because the defensive competition is not good enough to exploit their mistakes. Even in top-level college games, they're playing against kids that have zero chance of playing at the next level. When they get to the professional leagues EVERYONE is really good. The "walk-ons" and "weak links" don't really exist in the NFL.

If these college QB's haven't mastered the study habits necessary to understand NFL defenses and and embraced the mundane aspects of the weekly"grind", they may survive in the NFL but they won't truly excel. Cam Newton comes to mind.