Nobody is great at everything. The world would just be so unfair if that were the case.
Therefore, chances are that if you're a superstar athlete who makes millions of dollars per year playing basketball/football/etc., you're not the greatest rapper in the world.
Nelly once said that he grew up wanting to play Major League Baseball. But once he figured out that that was never going to happen, he turned his sights elsewhere and became a spectacular OK rapper.
Similarly, lots of professional athletes should have come to the conclusion that since their rap careers were hopeless, they should have focused their attention solely on athletics.
Unfortunately, they did not.