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He just happened to be born with the sort of brain that made him good at making money that way. Once he discovered his talent he also discovered he had the sort of brain that made him greedy, so he wasn't satisfied with enough to get by, he wanted more & more & more & more, never being satisfied with what he already had. So he honed his entrepreneurial talent, & probably got high on the thrill of the battles & his successes in them.