Paulus vs Freshman Quarterbacks

We hear about Paulus stepping in and starting after three years of basketball. Is maturity the key to playing quarterback?

Ever think you'd see a player who has been away from the game for three or four years go to a BCS school and start in his only season?

We see freshman come in and go through spring practice, summer workouts and fall camp and not even mentioned as getting on the field.  They've been in football condition probably four years  which is certainly different than Paulus, who  has been away from the game.  Is he a super athlete, or proof that being in top level competition is more important?

We see teams sign 4 and 5 star quarterbacks but instead of playing them, suffer through offensive inablities blamed on the three or four year player.

What's the reasoning?