This is likely related to trait Openness to experience, which is positively correlated with IQ. Those with a better ability to assess ideas on their merit don't

This is likely related to trait Openness to experience, which is positively correlated with IQ. Those with a better ability to assess ideas on their merit don't need to develop as much of a memetic immune system, since their formative experiences contain much fewer learning examples of getting burned by malign ideas. And similarly, I think there's a good argument for wanting leaders with lower Openness than is commonly found among those with very high IQ. Obviously you want your leaders to consider new ideas, but you definitely do not want them to get carried away by any pipe dream that comes across their desk. Instead, you want their opinions to be pretty well fixed. That way, if you figure out that their values are aligned with yours, you can rely on them to stay true.