Why would IQ be explained by wealth inequality? I thought the literature was pretty conclusive - there's a benefit to rising above poverty but beyond that wealt

Why would IQ be explained by wealth inequality? I thought the literature was pretty conclusive - there's a benefit to rising above poverty but beyond that wealth doesn't buy much IQ. Poverty rates are falling, I'm not sure we would expect a person whose nutritional needs are met to be more or less smart because someone else is fabulously wealthy.