I was a manager, in addition to being a technical specialist, for a long time. It was a fairly small, highly-skilled team. As time went on, my management duties replaced my technical ones, and I was forced to do technical work on the side (open source work), in order to maintain my technical edge. This resulted in my having a fairly significant technical portfolio, by the time I left my job.
I have encountered very few good managers, in my career. I have seen some great technicians destroyed by becoming managers.
I think the industry’s refusal to cultivate lifetime technical careers has resulted in a lot of problems, but it is not anything that has been studied, in any meaningful way (of which I’m aware). I only have personal anecdata, which, by itself, isn’t particularly relevant, in the big picture.