The battle among billionaires for bragging rights as the world’s richest person got heated on Wednesday with the surprising surge of an old contender: Larry Ellison. In a stunning few minutes after markets opened, stock in Ellison’s Oracle rocketed more than a third, enough for him to temporarily wrest the title from its long-time holder Elon Musk and hand it to the software giant’s co-founder. But the stock market is fickle, and Musk was back on top by the end of the day, according to...