There is a characteristic not mentioned that can determine if someone will reach a high level or not. Self gratification or the ability to delay self gratification. The "marshmallow kid", even a gifted kid that cannot fight their own human condition to seek a dopamine reward from eating, entertainment, etc can't reach their potential. If you got a reward from problem solving and knowledge acquisition then it wouldn't take much to focus.

Why can we focus for hours gaming, but when it comes to solving a math problem, most of us will never start or stop shortly after.