Given that many environmental conditions to which exposure (in many cases, particularly early childhood exposure) demonstrably adversely impacts intelligence are more likely to be avoided with wealth (that is, both inversely correlated and with a clear causative mechanism for that correlation), this isn't at all surprising.

Can you cite a source for this?

I can see how it might follow from the assumption that intelligent people are more likely to succeed in their careers but keeping the GP in context, it should also be noted that not all intelligent people succeed because of various factors.

But there does seem to be a correlation between IQ and income. https://thesocietypages.org/socimages/2008/02/06/correlation...

This latter correlation could be explained by the wealth of the parents, as IQ may be a cultural artifact and income is correlated on education.