Yup. The majority of leaders I know are just average people who are more comfortable being assertive. Often aggressively to shut down nay sayers. Listen in meetings and hear how the people talking are normally not the most correct or the right ones but the most assertive.
Yup. This is often why smaller companies are dominated by poor leaders as well. There may not be many that many other voices and the non assertive people realize they are not being valued and leave or they don't join to begin with.
The later I get in my career the more I realize I care a lot about who my manager will be.