Business under Trump should thrive like never before, says Ray Dalio, the billionaire chairman of the world’s biggest hedge fund firm. Trump’s cabinet of former executives and dealmakers could spark economic growth well beyond what could be expected from tax cuts and new spending priorities alone, by infusing investors with renewed confidence, Dalio says. This summoning forth of “animal spirits”—a term coined by John Maynard Keynes to describe investors’ impulse toward action—could unlock the estimated $70 trillion in cash sitting on the sidelines as investors await higher returns. “If this administration can spark a virtuous cycle in which people can...