I agree, the causation is likely due to the fact that kids who are good at playing chess early on keep playing chess, which by default gives them years of addit

I agree, the causation is likely due to the fact that kids who are good at playing chess early on keep playing chess, which by default gives them years of additional training and experience more. As opposed to someone who has only started at 18, they are going to have a hard time competing not due to their intelligence or genius-factor, but lack of training.