In my corporate years, I worked under a lot of different Project Managers, some very good ones, some very bad ones, and many in between. I got to appreciate the skills needed. And I got to be a project manager myself several times. I was a bad one; not the job for me.
Good managers don't really need to have a deep understanding of the technical side of what they are managing. Having too much technical knowledge can lead to bad management. That was my problem.
A manager's job is to get the overall project completed, within the schedule and budget given to them by their bosses, and an acceptable quality level. The best managers are very good at constant communication with all of the people under their control. The engineers, shop workers, secretaries, and janitors all trust them and are free to talk to them. They provide tips about problems coming up, long in advance, that might slow things down. If the problem sounds realistic, the good manager gets the right people together and stands back. Let them argue out what to do to prevent the problem, then quietly approve their decision. Bad managers go off and decide what to do themselves, then surprise their people with their decision.
That's what a Manager does. A constant stream of talking to everyone, getting them to identify and solve problems before they grow, having them make the decisions (and get the credit). Then the Manager sits in front of his boss with a smile and reports that his project is on schedule and on budget. And the boss smiles. The best Managers seem like they don't do much of anything all day, except chat with all their people and commend them for doing a good job. And report to the boss. But they are doing a difficult and critical job.
Like I said, I have a lot of respect for good Managers. Because their job is not as easy as it looks. I know from experience.