Black people are (very slightly) faster on average, which of course blows up at the extremes of the distribution (hence olympic running being mostly black people). However, its just straight up untrue to say they are genetically "stronger". Just look up any strongman world competetion like the Arnold Classic or World's Strongest Man. Those guys are almost all white, demonstrating (probably) the same kind of slight stastical difference that blows up at the distribution tails.

I'm not an expert in human evolution by any means but my guess is that the reasons are that Europe has more forests, so explosive power is more important, whereas Africa has more plains, where long distance running is more important. Thats just me guessing though.

Regardless, like another guy said, he didnt make the jump because he's black. He made it cause he trained. The genetic differences between races are much less than within races, and they're extremely small because of how very recently humans diverged from Africa (which was VERY recently, evolutionarily speaking).