He's Nigerian. They build them differently up there, so his build isn't really a red flag to me.
We get a lot of them around here, mostly drug dealers. And they're usually huge, big-built MFs.
From what I know, the Nigerians who go to Europe and North America tend to be middle- to upper-class and are very successful. Doesn't surprise me at all that a Nigerian would excel in athletics. They tend to excel across the board.
ETA: Everyone pointing out that he's spent more time in America; it doesn't really matter. Even if we don't get into a discussion about genetics, Nigerians are a ridiculously proud people. And whatever they do, they tend to do it: A) with a certain amount of class; and B) with excellence.
That's the culture from which he hails. I'm sure he's been influenced by his American upbringing, but his family is Nigerian, and he will have been strongly influenced by their cultural background.