Starbucks offers a useful warning about the difference between understanding how businesses work and knowing how to make one work. During Laxman Narasimhan’s 17 months running Starbucks, the company lost about $32 billion in market value. Its share price fell almost 24%. Then Starbucks canned him. There’s an interesting backstory. Narasimhan spent 19 years at McKinsey, eventually becoming a director. He later held senior roles at PepsiCo and became CEO of Reckitt before Starbucks recruited...