I have been fortunate to know a number of extraordinarily smart folks. Some have amazing careers. Some not.
Started with my father, who was a brilliant theoretical physicist. He was reading the NY Times at age 3 and grew up in a poor family – his parents were immigrants. I don’t think anyone thought to accelerate him in school. His peers were some of the best and brightest in physics. Feynman used to come to our house when I was young and played the bongo drums, though I don’t really remember him. But, I think I know four other Nobel prize winners from my father’s colleagues.
I know someone who got his Math PhD at Harvard at age 19. Very smart. Good career but not amazing. Always a bit brash – sometimes a bit of braggadocio. We had over for dinner another person who was homeschooled by his father, who apparently just drove around North America with him and would stop in at various universities. Joined the MIT faculty at age 20. Remarkable talent. Very modest. Oh, for CC points of reference: this person never attended an Ivy League school. Both clearly prodigies, but I’d say one is having more impact than the other.
At the end of the day, I think internal psychological drive and good choice of problem areas really matter a lot in terms of extraordinary success. Maybe also a good support system as a young adult.