Factors that dictate any RB getting 2000 yards.
1. An excellent OL that plays hard from start to finish.
2. A Defense that can stop the opposition regularly.
3. A QB that can manage the game and not lose the game.
I am sure there are others. My point being that a guy like Walter Payton didn't come out and say "I am getting ___ yards" He would let the game dictate his yards. I would say it was his luck to play while the Bears were playing some tough D.
We are all born ignorant, but one must work hard to remain stupid. Ben Franklin