How did warren buffet become a billionaire?

The deals that he talks about the most in his various speeches and interviews which you can find on youtube is the AMEX salad oil crisis and the Geico investment. With AMEX, everyone figured AMEX was done for when they invested in salad oil which turned out to be a warehouse full of oily seawater, the core business operation was solid, it was just that the company was taking a huge one time hit that many figured it would not survive so Buffet invested at bargain prices. With Geico, he bought the shares from his mentor Ben Graham, the business was solid but the management was ineffective however Buffet could buy enough shares to replace the management with more effective staff and the company took off from there. Basically he invested in businesses that he was confident would do well when others thought otherwise. He's taken aggressive positions that are as much as 40% of his total worth but never everything. He's actually very conservative for the most part and only aggressive when he is certain of the outcomes. He appears to have a knack for evaluating a company's prospects and for sizing his investment accordingly. He doesn't always win with his investments but he never loses more than he can afford to lose.