although genetics play an important role at who wins during their developmental years, i think it is equally true that someone who trains hard and just doesn't allow themselves to fail can run just as good. for example, there are many stories of runners in the 40's - 70's that ran as hard as they could then went on to be world champions in their late 20s and 30s. a more modern day example would be like clayton murphy who ran 4:20 and 1:58 or so in high school to do relatively well in college and run 1:54. Then go to the olympics and medal!
All I'm saying is, genetics and being gifted only get you so far. Look at people like Grace Ping, or any young world record holder for that matter. Google the world records for every distance at age group levels and see you will never hear from these talents later on unless it's around the U17-U18 mark. That Jakob Ingebrigsten guy? Probably will break 4 a couple more times and might be as good as his brother, but probably won't get much better than he is right now. On the other hand, that 4:30 senior miler might go on to do great things if they work hard enough, despite having no runners in their family, too short, too tall, "no speed" all these things don't matter and it comes down to who wants it more.