​​​​​​​Mukesh Ambani overtakes wealthiest European to become world’s fourth-richest person. India’s richest person has already surpassed some of the biggest tycoons in recent weeks -- a list that includes Silicon Valley titans such as Elon Musk and Alphabet Inc. co-founders Sergey Brin and Larry Page, as well as the so-called Oracle of Omaha himself, Warren Buffett.