I've been on both sides of the desk with a major corporation. I was a tech that worked on electro/electronic-mechanical comm equipment for seven years. I went to school at night and got an Associate's degree in business management and wound up being the lead technician. Not tooting my horn but I was very good at what I did. Management selected me to go to through a one day management assessment ordeal (role playing, etc.) and I guess I did okay because I was promoted from hourly to 1st level management.
I had to move (it was the policy) and I was thrown into the fire supervising my first crew. It was a real struggle and extremely stressful, I would be at my desk at 0630 hours to organize work for the crew and I would stay until the last guy came in (usually 1800-1900 hours.) Saturdays I spent at least half a day at my desk catching up on paperwork. The company sent me to various schools which helped me learn how to be an effective manager.
I had zero control over the work that came in to my crew, every morning was a new adventure and my boss expected everything to be completed on the due date. No excuses which added to my stress level but I persevered and got another crew a few months later that had older and more experienced guys. It was a good bunch and we had a good working relationship. I respected them and they knew what I expected - quality work done by the book except in very unusual circumstances. I had to inspect every guy's field work twice a month and if something wasn't done right I would show them the problem.
My guys were union represented which was never a big issue for them (and the shop steward) or me. I treated them as I would like to be treated and that was that mostly. Once in a while I would have a guy that would not or could not go with the flow for various reasons. I always made sure we didn't have a training or personal issue which impacted their work. I had one guy that was a good dependable troop and all of a sudden he starts to get argumentative and didn't perform to expectations. Long story short he had a brain tumor (he was in his 40s) and went on disability. Every two weeks I had to take his paycheck to his house (company policy when on disability) and I watched him slowly decline. It one of the most difficult things I've ever had to do.
In every crew (anywhere from 8 to 12 people) I had, I always had one person that took up 80% of my supervision time. One guy had such a poor persona I made a job for him where he didn't come into contact with any customers - no telling how much damage this guy did before I sequestered him. He really should have been fired but that would have been a long struggle for me, the crew and my boss.
Ultimately I got out of having direct reports and got a staff job and moved again (for the third time), more night school finishing up my Bachelor's and then a Master's degree. Another promotion. A good career but I paid my dues.
Are there lousy managers out there - of course. Just because you are good being a tech or mechanic doesn't mean you have the skill set or capability to be a leader.
How can ANY boss be proficient at that job not knowing what it takes to perform it? Good luck with that!
