I think Youtube does this just to piss off people and make ad revenue off a whole crop of angry videos that are made.
It makes sense as a hypothesis, except that Youtube recently demonetized a wide cross-section of videos, including some from very large content creators. That probably cost them a lot more money than this single move will make them.
They actually didn't, just made the system to tell creators that videos were demonetized much better and instant. No rules or terms of service were changed in that.
