Not to take away from his achievements but like Sal Khan (who has done similarly with Khan Academy) he'd already made his money in investment banking before entering the tech world.
It makes a huge difference when choosing to go the non-profit vs profit route when you're already personally well off.
Eh, Sal Khan was a 30-something hedge fund analyst when he started Khan Academy. He's intelligent, hard-working, and could find work somewhere else, but he wasn't exactly "set for life" if the Khan Academy thing didn't work out. So don't let that stop you going the non-profit route!
It makes a huge difference when choosing to go the non-profit vs profit route when you're already personally well off.