All of the OP’s points could be said about church sermons as well, and yet there’s still thousands of church gatherings every week.
So I think your point hits the nail on the head. People don’t go to these large gatherings because they’re looking for a presentation of convincing arguments, books and recordings are better for that. They go to experience the sense that they are part of something bigger than themselves. They want to feel like they are contributing to something important, and a large crowd all in unison makes them feel that way. Rallies aren’t meant to change minds, they’re meant to get the base excited to donate/ volunteer/ talk to anyone who will listen.
Were they drinking soda in a lab room filled with fissile material?