In discussing intelligence and other abilities, and how they relate to performance and success, I have often taken the analogy of basketball because the attributes height, speed, and gross-motor coordination are all extremely important, but not equally so - and other attributes contribute as well. To succeed at the highest levels more than one of these is going to be needed, even if you have one in abundance. Consider Tacko Fall, who is 7'6", but even he has needed some hard work and engineering-level intelligence to overcome his lack of speed and general coordination. One could also use music as an analogy for similar reasons.
I have consequently believed that in the same way that height is the #1 requirement for basketball but is a threshold phenomenon, and after a certain point other characteristics take on increasing and eventually equal importance, that intelligence is the same in it's operation across a huge number of activities. Yes, one needs an IQ of 90 to get into the USMC, and probably 110 to be an officer, but beyond that other characteristics such as self-discipline begin to gradually take over as predictors of success. Certain hard sciences may have very high floors, up into the 130 range or even more, but even there the ability to work with others, the capacity for hard work, etc become of increasing importance.
That is at one level true, because IQ alone won't get you much. But the effect of the other characteristics such as the modern favorites "grit" (the Angela Duckworth book), growth mindset, EQ, 10,000 hours (with or without focused practice), or privilege - or the old favorites hard work, charisma, luck, training, or connections turn out to matter only a little each according to Michigan State researcher Zach Hambrick. Even at high levels of expertise, intelligence remains the best predictor of the ability to next level up. Not EQ. Not growth mindset. There does seem to be some sort of generalisable sales ability, but it has proven very tough to measure. which doesn't stop these guys from selling you theories about what it is and what works. Selling sales is big business.
I had expected a different result. But his methods seem good and the samples are large, including the ASVAB data in some cases. Hambrick is on the committee to improve the ASVAB and AFQT, and he is at pains to say that he thinks they are already quite good but could be better, not that the test should be discarded after 100,000,000 tries.
His explanation is not universally accepted, but this is always true in IQ research. People's priors are that something else, maybe anything else, should be true and there is motivated reasoning. Even I hoped that the hypothesis above would prove out and the starkness that g-factor is the single largest predictor in field after field would be relieved at least a little.
People do have trouble understanding even a two-factor model when it goes against their priors, and they immediately accuse one of claiming that those other things don't matter at all. No, it's just that they vary from task to task whether they are important, with little generalisation among them, and even at highest levels do not match intelligence. Speed in basketball is big, but not as big as height. Beauty is big in Hollywood, but sustained excellence over decades is better predicted by intelligence, as in Phi Beta Kappa Glenn Close.