Greg Miller, 48, learned a lot about the car business from his father, Larry H. Miller. But he is a very different leader from his dad. The senior Miller was a micromanager. The stress of that intense level of involvement, his son believes, led to Larry Miller’s death in 2009 at age 64. Greg Miller took over as CEO at the height of the recession. He faced the painful process of slashing costs and then growing the company. He adopted a delegating management style.