Genetics has a huge influence on what someone is predisposed to and what they can achieve. Certain ethnic groups and families, on average, are more likely to have certain traits and less likely to have others. But genetics doesn't matter , in that just because you have "bad" genetics doesn't mean you'll suck, whether it comes to weightlifting, intelligence, temperment, etc. Maybe you won't be in the top 0.0001%, but…
Kenyans, Ethiopians and (white) Americans are not genetically homogenous. Even two siblings can be quite different genetically. The great American distance runners have genetic talent - they didn’t just train harder than their middle school mates who were out of breath while the champions ran faster and longer than anyone else weeks after beginning training.
Who knows if it was only due to genes? And more importantly, there isn't a gene that's about running faster. (sure, some genes are helpful and might get you in front - not discounting the work the athlete goes through)
Getting to the podium is a mix of several characteristics: Some people might be more prone to muscle recovery/injury resistance. Another one has a better muscle fiber mix. Another one has different muscle attachment positions. And another one feels less pain.
Though yes your genetics probably will push you towards a sport. Take the 100m finalists and put them to train marathon (and vice versa) and they'll probably go to the back of the pack even with good training.