Musk is a "trillionaire" because of incredibly overpriced stocks.

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9. Of course Rockefeller

Ironically ended up making even more money after they broke up Standard Oil than he had prior. He was a large stock holder in all the companies that it was busted up into and when they started competing against each other...he profited from it all. I remember seeing an interview with his grandson or great grand son once, where they said than old man Rockefeller said something along the lines of "If I knew I would make more after the split up Standard Oil, I never would have fought it so hard."