Jack Dorsey — Twitter & Square/Block

Dorsey dropped out of NYU and co-founded Twitter — the platform that gave world leaders, journalists, and celebrities a direct megaphone. He was ousted, returned as CEO, then watched Elon Musk buy it for $44 billion. Meanwhile, he built Square (now Block) into a $40 billion fintech empire processing payments for millions of small businesses. Cash App alone has 57 million users. Dorsey is the only founder who built two publicly traded companies from scratch — and lost control of one to the richest man on Earth. His net worth: $5.5 billion. Not bad for a kid who quit NYU.