A social media spat between Elon Musk and Jeff Bezos this week underscored a sharpening rivalry between two of the world’s richest men at a time when both are trying to grow their sprawling businesses empires in President-elect Trump’s second term.

Elon Musk reignited a public dispute with fellow billionaire and space-industry rival Jeff Bezos, saying the Amazon.com founder had said President-elect Donald Trump would lose the election and that people should sell stock tied to Musk.