It’s not particularly surprising that the Jamaica has the top sprinters right now: track plays a larger role there than in other countries. Jamaicans love cricket, but they don’t play American football, they don’t play basketball, and they aren’t quite as crazy about soccer as most other countries. So the loss rate of sprinters to competing activities is low.This makes sense: what are your opportunities relative to other opportunities? Similarly, if you meet a male immigrant from India or China, there's a fair chance that they have a degree in engineering. So, naively, you might think that engineering is all they teach there. Instead, the case is that engineering is a way to a good job.
Then there’s nurture: sprinting isn’t hugely complicated, but it requires coaching, along with decent quality tracks so sprinters don’t get hurt. Jamaican athletes, who speak English, tend to get track scholarships to American universities, where they enjoy good training facilities.
Similarly, Jews in the middle ages gravitated toward banking because it was an avenue that was relatively more open to them and relatively less open to the Christians around them.