It's because positions of power attract people who desire power, not people who have leadership skills, and there aren't good metrics for what makes someone a good leader that you can use to filter out the bad ones.
See: Politics throughout the entirety of human history.
It is. As a leader myself, it's honestly embarrassing for my profession. I really don't get why it happens. Personally, that kind of basic shit is dealt with swiftly in my company. Leadership isn't rocket science.
