There are lots of ways you can be brilliant but you can test raw logic, ability to work out solutions, maths, general knowledge and some people just are pretty good at that sort of thing. I always seemed to absorb what I heard and read and got very high IQ scores. I am not sure it is all learned. Some of it is just inherent. It's about speed of brain power, being quick and it's not that you're coached for it. You're just (some people anyway) made like that.
Bright children do not always end up earning a lot or even necessarily succeeding in school exams and some fall by the way side but plenty do . If you did IQ scores of the most successful people in many walks of life I bet they would be pretty high in all kinds of fields of achievement.