Elon Musk just learned a hard political truth: that even the richest man in the world cannot buy influence in Washington, at least not when it matters most. Musk can buy recognition in D.C., and he has, complete with a steady stream of free media every time he spars with Donald Trump. But despite pouring hundreds of millions of dollars into election-related causes, endorsing candidates, and even threatening to primary Republican lawmakers who supported the “Big Beautiful Bill,” Musk was left empty-handed. Congress passed the bloated spending package anyway. Republican members shrugged off his influence, ignored his warnings, and fell...