Mattress Firm has three stores in Austin, Texas, within half a mile of one another. In Winston-Salem, N.C., it has two stores with identical hours at about the same distance. Schererville, Ind., (population 28,701), once had five shops less than a block apart. While retailers across the U.S. were shuttering outlets and more commerce was moving online, the mattress company was bucking the trend, going from about 700 locations to 3,500 in five years before filing for protection from creditors last month. Was it the breakneck growth alone that landed Mattress Firm Inc.