Other factors can be demonstrated: for instance socioeconomic status has an impact on which kids are doing what as they grow up which itself has an impact on who makes it to professional level sports.
There are also different sort of racial components at play: is the reason why there aren't any white NFL cornerbacks because there aren't any white athletes capable of playing NFL-caliber cornerback? Or is it because white kids with a certain athletic profile wind up as slot receivers in high school while black kids with the same athletic profile wind up as defensive backs?
That is at best *an* actual reason.
Other factors can be demonstrated: for instance socioeconomic status has an impact on which kids are doing what as they grow up which itself has an impact on who makes it to professional level sports.
There are also different sort of racial components at play: is the reason why there aren't any white NFL cornerbacks because there aren't any white athletes capable of playing NFL-caliber cornerback? Or is it because white kids with a certain athletic profile wind up as slot receivers in high school while black kids with the same athletic profile wind up as defensive backs?