When a developer becomes a manager, It’s not a promotion, it’s a career change:
If you want to do your leadership job effectively, you will be exercising a vastly different set of skills on a daily basis to what you are exercising as an engineer. Skills you likely haven't developed and are unaware of.Your job is not to be an engineer. Your job is not to be a manager. Your job is to be a multiplier.
Don’t miss the section on how we undervalue non-technical skills. It’s not unlike developing software, it’s just that your levers are people and processes instead of software and data centers. See also, Managing Humans.