I never once had a manager who even pretended to be a coder, and I've worked for a wide variety of companies ranging in size from a few people to tens of thousands. The only technical manager I've ever witnessed was myself when I managed teams of developers (and that only happened by accident when I wasn't really paying attention). Even then I was less of a technical manager and more of a lead developer who also took on management functions because there was nobody else around to do it.

It certainly seems like a manager with actual technical skills would make the best manager of a team of developers, as long as they also have the people skills to do it. And didn't harbor the desire to fire everybody and just do everything themselves - like I did.

or was it that they hired “career managers” whose only skill was to organise things?

My best manager was a former dentist who quit the profession after just two months because he couldn't stand the idea of sticking his hands in peoples' mouths all day long. I don't think he had anything resembling formal qualifications for management.