My guess would be a lens artifact like a scratch.
This would be a fixed camera on a tripod. The moon would continue to move across the sky to the right making it appear as though the scratch is moving to the left.
The video editor zooms in and out on the artifact making it appear to move in relationship to the moon.
That makes a lot of sense!
“Hey Bob, lets put a scratch on your $200 lens and get some youtube hits! Hold my beer!”
(Or more likely an already scratched lens - or perhaps some water-based marker drawn on as a spoof?)
Stuff like this is so interesting. Brings up the various levels of knowledge of people (photographers vs. non), and also the beliefs of people. I’m with Fox Mulder in “I Want to Believe” as it is sort of cool to think of ET’s and Bigfoots, etc. So 50% of the time that shadow in the woods is “Yeah - that could be a bigfoot”, and the other 50% of the time is “I don’t know - there’s just something not right about that.”
Especially with “ghosts” - there always seems to be a photographer or somebody with a good explanation of lens flares, cloudy lenses, etc.
And you get all sides of the knowledge and beliefs right here on FR!