A manager requires very different skill sets from a low-level developer. However, for your senior developer, you need very similar skills as a manager. The manager can skip all the engineering skills, but the senior engineer cannot skip all the manager skills.

Senior engineers and above, they need to know all the engineering skills, but they are most of their time not being engineers, they're being a people person. They're talking to others, they're explaining to other developers what's going on, how to do their job. There is somewhat difference as the manager is thinking only about the organization structure and how good people are, whereas the senior engineer is thinking about how to use people to make the engineering parts better.