Why are audiences tricky to work with? We misunderstand what is happening when we are in the audience. Audiences have blank faces when they listen. They listen passively

I work a lot with people who are anxious around public speaking. One thing is very clear that we think far too much about it. Especially if we are scared and anxious when we are the centre of attention. And guess what? The overthinking about public speaking does not help

What exactly does it take for people to get confidence? Do we understand confidence in a useful way? What actions, beliefs and understandings do we need around confidence for public speaking?