Tim Cook is the ultimate non-founder success story. As he steps down as Apple CEO after 15 years, that's the biggest takeaway for me. Silicon Valley lauds founders as the only leaders capable of creating huge, disruptive, and lasting value. Cook blew this " founder mode" theory out of the water in spectacular fashion. I was there at the start. When Steve Jobs died in 2011, I went to Apple headquarters to report on the scene. Underneath the grief, questions lurked. Would the company be OK