They don't.

Don't believe even for a second that this guy is rolling this clip in front of an actual audience.

And if he does, don't believe even for a second that this guy didn't personally handpicked an audience or place of anything but actual Christians.

This reminds me of a colleague course where our lecturer ordered us to go to a speech about some eco bullshit held in assembly hall. With the exception of some two old folks and our group who couldn't give less of a shit, the guy who was given the speech would be literally talking to an empty hall.

I suspect this is a same thing and the echo effect in the video is edited to make it look more legit than the actual bullshit that it is.

They don't.

Don't believe even for a second that this guy is rolling this clip in front of an actual audience.

And if he does, don't believe even for a second that this guy didn't personally handpicked an audience or place of anything but actual Christians.