(Einstein would have had an unexceptional score on an IQ test, had he ever taken one. His schoolteachers thought him destined for failure.)
To put it another way, polymaths are unusual but idiots are everywhere. And people who are outstandingly good at say, computer engineering can be mediocre at philosophy or business administration.
Psychometrists distiguish between crystallized and fluid intelligence. Expertise is a combination of knowledge and ability. But ability itself is multifaceted, and raw talent goes untapped without the motivation to study and the opportunity to work.
For most areas of human endeavor, being smart enough is all that is required. Being a genius helped Albert Einstein reimagine physics, but did not make him a better patent clerk.