Ironically IQ is also popular amongst people in a very different situation, that is, people that aren’t actually successful “in the real world” but score highly on aptitude tests. Their high scores serve as an identity pedestal to look down upon others and set themselves apart from the masses. This seems to be the primary demographic of IQ-requirement organizations.
Now of course there are scientific studies on this topic, but let’s not pretend like this is a cultural meme because writers like Cremieux are just tirelessly searching for the truth, no matter what ideological consequences that may have. They quite obviously have a viewpoint first and then work backwards from there to justify it.
As a meta comment: the whole obsession with IQ as a kind of unchanging permanent quality seems very much out of tune with how biological systems actually work, and is kind of a remnant of a Platonic worldview. That is, it’s not dynamic/process/system oriented in the way that nature actually works, but instead is in search of eternal qualities á la Plato.