Because lower IQ people are more or less rational. It is easy to have casual conversations with them and not think them especially lacking. This is why people who disparage their capabilities in any way seem like “racists” and why “oppression” seems at first like the best explanation for their consistently poor fortunes. Their deficiency manifests most greatly not on an individual but a group level. The scions of the Enlightenment ultimately abolished the group and therefore regard the study of the interaction of collectives in aggregate as a mortal sin. This neglected and most important of the social sciences, which all advertising and electoral politics are steeped in, is an open opportunity for dissidents of all stripes.
Funny how many people are willing to concede that large groups of people are being exploited. Many others are willing to concede that large groups of people are less intelligent than others. Yet the respective prejudices of both are challenged when one dares to suggest that large groups of unintelligent people are being exploited precisely on account of their lower intelligence. The very mention of this notion pricks up different tribal hairs... One sensibility's egalitarian conscious will immediately double down on the idea that low intelligence is an effect of exploitation and another sensibility will become paranoid that one's own potentiality for exploitation amounts to statement about their own intelligence. Nevertheless, low intelligence isn't the only bad hand, unfortunately.