As Donald Trump took the oath of office on Jan. 20, he was flanked by some of the world's wealthiest people. The billionaires present that day " including Elon Musk, Jeff Bezos and Mark Zuckerberg " had never been richer, flush with big gains from frothy stock markets. Seven weeks later, it's a different story. The start of Trump's second term has delivered a stunning reversal for many of those billionaires sitting behind Trump in the Capitol Rotunda, with five having lost a combined $209 billion in wealth, according to the Bloomberg Billionaires Index.