Speaking on stage during Mr. Trump's inauguration as US president, Mr. Musk described Mr. Trump's victory as an event to secure "the future of civilisation" and thanked his supporters for making it happen. "This is what victory feels like, this is an extraordinary victory," said the world's richest man and a Trump mega-donor. "This is a fork in the road for human civilisation." Mr. Musk then gave an energetic salute to the audience, but the move quickly went viral online, with some critics comparing the gesture to "Sieg Heil" (an old German greeting meaning "long live victory" that was once used as a slogan at a Nazi party convention). This is not the first time Mr. Musk has drawn attention for his onstage mannerisms, after Mr. Trump sparked controversy at his second rally in Butler, Pennsylvania, with a "dark MAGA" cheer.