Other comments here have pointed out that the drop is likely due to a periodic cleaning of bot votes, against the blog author's premature, sarcastic insinuation

Other comments here have pointed out that the drop is likely due to a periodic cleaning of bot votes, against the blog author's premature, sarcastic insinuation that some nefarious manipulation is being performed at YT (there is, but it's not nefarious but to combat third-party manipulation that misleads the user and abuses the platform). Perhaps it is also of note that the author performs a naive analysis of limited climate data in a linked post to draw a conclusion against climate change.