One of the common conceits in leadership is that nobody is truly essential for a company’s continuity. I call it a conceit, but I do mostly agree with it: I’ve felt literally sick after hearing about some peer’s unexpected departure, but I’m continually amazed at how resilient companies are to departures, even of important people. About two-thirds of Digg’s team left in layoffs in 2010, but we found ways to amble on. Much of Uber’s leadership team turned over in the 2017 era, and it was chaotic,...