It's a mix of intelligence and privilege. You only need to be just smart enough to take full advantage of said privilege. IIRC nobel prize winners have a median IQ of 120. You don't have to be that smart to win a nobel prize, but damned if it doesn't help to have parents to back you every step of the way through your education and training, and the sympathetic ear of a rich and connected network of peers and friends to help you secure grant money.