If I were to guess the decreased views were merely the fallout from YouTube vs. adblockers. It's as simple as that.
YouTube tried to implement measures that hindered adblockers, and adblockers implemented measured to counter it.
The cause of this was decreased viewership for many channels centred around gaming and technology. People who view these channels are a little more tech-savvy than most, such as people who watch make up artists and fashion shows. I happen to watch both and only these gaming/tech channels have seen a sharp decline.
It will all come to equilibrium in a couple of months again. These people are crying about literally nothing.