A lot of time success in anything stems from knowing one thing in particular very well, at the sacrifice of not knowing a lot of general knowledge.
For example...sports. Particularly football. Learning an NFL Level playbook would take someone that never played the game months, possibly years, to comprehend. But even the seemingly most unintelligent athlete can switch teams, and get the playbook down in a week.
Often it's a matter of it being the only thing they know.
Silly example, but I think of the stories about Vince McMahon. It's widely known that his pop culture knowledge doesn't go beyond what was popular in the 1960's and 70's, but (controversies aside) he ran his business to the point where it was valued at $5.5 Billion when he stepped down.