I met a genius that worked in the shipping department of the first software company I worked for. (Back when people shipped software.)
But working in the shipping department was only what he did in order to persue his passion, which was bird watching and photography. That is where he expressed his genius, although he couldn't make a living from it, it made him happy.
There's a great deal of the population who spend their lives working in shops and so forth doing relatively menial work. Why they're doing it is not about intelligence at all, it's all about drive.
A driven person who's terrified of Maths and Sciences is unlikely to become a leading Physicist, but they might well power through enough basic sums to successfully establish businesses.
An intelligent person who's not driven might never achieve anything like fame, at least in their lifetime, but they still probably enjoy their free time and passions.
There are plenty of people doing "menial" work who have plenty of drive. The work is to earn a paycheck and their life isn't about that. The drive is centered on something that doesn't earn them a living (e.g. family, bird watching). Not everything in life is about work and money.
But working in the shipping department was only what he did in order to persue his passion, which was bird watching and photography. That is where he expressed his genius, although he couldn't make a living from it, it made him happy.
Reminds me of http://en.m.wikipedia.org/wiki/Wilson_Bentley who first photographed snowflakes. His genius never gained him fortune.