The Oscillations might be down to the Northern / Southern hemisphere.
At peak, the Northern Hemisphere are watching, as they go to bed, it becomes morning for Australia, or visa versa, simply people watching the video's from different time zones...
Could that be it? (eg, 9am regardless where you live, you wont watch it, by 12pm-1pm you might and certainly come 6pm, when most would watch) now repeat again across all the time zones,
but that large spike ? at the end, is that a bug?