Knowing, in isolation, that IQ is more closely correlated with income levels in childhood than IQ is with thing X, does not imply that IQ is not a causal contributor of X.
It could just be the case that IQ is partly genetic (in fact, it is) and that IQ may be a causal factor in income levels to a stronger degree than it is for autism or other things.
It could just be the case that IQ is partly genetic (in fact, it is) and that IQ may be a causal factor in income levels to a stronger degree than it is for autism or other things.