I think most can agree that genetics, specifically ones I.Q., has an effect on chess. In fact, I would be surprised if any of the 2800 players did not have a genius I.Q. The question is, how big of an effect does gentics have on chess? Like how much harder would somebody have to work if they had an I.Q. of 100 versus 160. I doubt that there isnt a correlation between IQ and playing strength, but who knows? Maybe it's all just hard work.
Talent and hard work are what is required to succeed at the highest levels of anything. Talent by itself will not do it and neither will hard work without the born talent.