You need muscles to lift weights and you also need things like bones. Does that make the idea that you need muscles wrong?
No, but that doesn't mean that it is the total and unique factor that will yield a definitive correspondence. Of course in the case of something as simple as lifting weights it is more important (and obvious) than in an endeavor such as chess that requires a wider range of talents
Anyways I think it's not a question of intelligence but the capacity for work you can enjoy putting in and that dosen't feel like work but like you are doing what you like doing, and you can do it for many hours on end...
Those who were mature enough to reach this level of seriousness and passion, combined with work ethic, at early age become prodigies (in chess, music, math, anything)
Prodigies are those children who show an unusual aptitude for something and so are encouraged and trained in that field. No one knows the way it occurs; probably the way their neural pathways developed are unusually well-suited for the thought processes inherent in the understanding of the subject. Five-year-old Aram Khachaturian had just started piano lessons when he displayed the ability to play a piece he had just heard and compose some variations on it. There are rare individuals like this that just seem to pick up math or music or chess "at first glance".
As for work (even if it is fun for someone) being the key, remember that chess prodigies Capablanca and Spassky both admitted to being lazy and not bothering to study the game much. And there are people who can solve difficult, multi-step math exercises in their head faster than they can be typed into a calculator. No amount of work will give most mathematicians the ability to do this.
I'm not saying dedication and work are not helpful, but they don't provide the total explanation.