Was he playing into a PA without a foldback monitor?

That can be a really disorienting experience. As the performer, you can't hear the volume of sound that's being thrown at the audience. But the audience hears a sound level high enough that they think it must be drowning out normal conversational speech. It does - for them. But not for the performer behind the speakers. They're only hearing their own *unamplified* sound level, and anything you say comes through to them exactly as if no electronics were present.