The world’s richest man led the charge to kill a bipartisan spending deal, in part by promoting false and misleading claims about it.When President-elect Donald J. Trump picked “the Great Elon Musk,” the world’s richest man, to slash government spending and waste, he mused that the effort might be “the Manhattan Project of our time.” On Wednesday, that prediction looked spot on. Wielding the social media platform he purchased for $44 billion in 2022, Mr. Musk detonated a rhetorical nuclear bomb in the middle of government shutdown negotiations on Capitol Hill. In more than 150 separate posts on X, Mr....