I think people's eyes are just naturally drawn to faces, so more people end up seeing the thumbnail among the grid of other videos, and are more likely to watch the it as a result
That's the base narrative, but I find it difficult to believe without proper controlled testing. People are 25% more likely to click on a technical video when the creator is trying to look like a buffoon? It just doesn't sound correct.
People don't click on the video because of the dumb face. They watch the video if they think they'll be interested in it. But the dumb face makes it more likely that you will initially notice the thumbnail
