You wouldn’t put a blacksmith in charge of an army, even though he knows a lot about weapons. You wouldn’t put an accountant in charge of a sales team, even though she knows a lot about revenue. You wouldn’t put a baker in charge of a restaurant supply chain, even though they know a lot about food.
Subject matter expertise isn’t the same as scope, philosophy, and people management. It’s great to have both, but in a pinch, skip the subject matter expertise. Smart people can learn and rely on experts, but it can be nearly impossible to make a general out of a blacksmith.
The Opportunity Machine 