As the heads of leading artificial intelligence companies came together last weekend to warn that runaway AI development could lead to catastrophic outcomes, momentum briefly seemed to be building for regulatory action from Washington.But one connected and influential tech industry figure has become the leading voice opposing many proposals for government action — on his podcast, in media appearances, and in his private advice to President Donald Trump, who now calls AI doomsday fears a “hoax.”David Sacks is a venture capitalist and part of the “PayPal Mafia” who, in recent years, has exemplified the rightward shift of some in the...