I’ve been working for more than 30 years. I was seriously demotivated by managers, but never motivated by them. The beat I got was protection from them to give me free space to work. But the motivation was always internal.

Being a manager myself, I never got to motivate anybody do anything they didn’t want to. If they wanted to, it worked, but the motivation AFAIK was internal.

Of course that is one person speaking. Milage can vary.

I think you can indirectly motivate, or is that something else? If you create a good working/team environment and reduce the factors that demotivate people, then you will indirectly motivate them. This includes working on yourself as a manager. There are of course edge cases, but most people will thrive if the environment is good.

I want to hazard a guess that a motivational manager is just like a well-oiled cog in a machine. You essentially never notice them as having influence over your motivation and only pay attention to the squeaky and rattling and faulty ones.

You're making a nuanced point but it's correct. Good managers can give a little motivation (mostly by talking about and finding the right areas to work on for those people that don't otherwise already know). But for the most part good management is buffering the core that allows individuals own motivation to be self-sustaining (and productive over time) and also making sure that people aren't on a path that won't be useful (i.e. the manager knows the company will never fund phase 2).