Here’s an interesting study that concluded that math and reading skills trumped many other factors determining socioeconomic status.
I also think that intelligence has to be measured according to Daniel Goleman’s Theory of Emotional Intelligence
There is so much that goes into success in the professional world other than IQ. As others have said, the motivation to have money,to strive for financial success. Is the person comfortable with little and therefore unmotivated to sacrifice time and effort to making more money? Do they already have enough to feel “comfortable”?
Also, social skills and personality factor largely, in some fields more than others. The opportunities of education and home environment are sometimes a major factor too.
I think it’s important to find the right fit between aptitudes, predispositions and weaknesses. Some people are lucky and find the right profession and the right position, that is, the “right fit”. Others seek it all their lives and their talents go to waste. A real shame. With a little guidance some people would do so much better. For others, a personality transplant might work, lol.