For a few weeks in late January and early February, the U.S. economy seemed to have reached a rare sweet spot. Inflation was steadily slowing from painful heights, and growth and hiring remained sturdy despite rising interest rates. Perhaps, the thinking went, the Fed’s inflation fighters were managing to nail a notoriously difficult “soft landing″: A scenario in which borrowing and spending slow just enough to tame inflation without tipping the world’s biggest economy into a recession. Then something went wrong: Inflation resurged, and with it fear that the Fed might have to raise rat...