Here’s the video....now note up close and you’ll see this rapid movement...
https://www.youtube.com/watch?v=rTnKsKnGhn4
The 2:07 mark at the video you posted is scary, too.
Not only is full-sceen mode helpful in viewing, but YouTube also offers slow motion playback. By clicking on the settings icon at the bottom of the viewer, and changing the speed from normal to .25, one can easier see what we’re talking about.