"they'd just need significantly more innate intelligence, which is a very tall order." I dispute this. Ramanujan is by all accounts on Von Neumann's level and

"they'd just need significantly more innate intelligence, which is a very tall order." I dispute this. Ramanujan is by all accounts on Von Neumann's level and so his example seems to disprove this statement. Or maybe you think Ramanujan has "significantly more innate intelligence" than Von Neumann? It's possible, but without evidence, and a bit farfetched. I think wealth helps but through a different mechanism to what you're thinking. Avoiding malnutrition is the big one. A secondary point is avoiding the need to work and being able to focus on intellectual passions, which many average-wealth people can do. Adding more money to the picture doesn't help beyond a baseline. Ramanujan was fairly poor but still had enough family wealth to be able to eat enough food and dedicate a lot of time to his passion.