Point of fact: chess is learned but only to a point, probably around 2100-2150 ELO. That is the limit of what most people can accomplish with a lot of study and hard work.

Pushing beyond that and into the Super to Elite Grandmaster range (2550-2800) requires extraordinary levels of memory, concentration, calculation and pattern matching. Levels that can't be instilled in someone through any amount of training. A person either possesses them or (s)he doesn't.

I lack the evidence at hand, but I'm certain I've seen it before that aptitude in those areas correlates strongly to high intelligence.