Quoted from kermit24:If the license holder approves of having a demonetized video on YouTube, why wouldn't YouTube allow it?
because of their own machinery. Artists, Management, Labels, all have a seat.. and usually outsource enforcement of their rights to 3rd party providers who make a business out of doing this kind of policing at scale. It's heavily automated and there can be many stakeholders involved even over a single recording.. or even more common... derivatives of the same recording. (imagine a studio recording, a live recording, a compilations album, etc etc etc).
So with all these moving pieces... it can actually be difficult to ensure valid or approved uses don't get caught in the net and marked for takedown by a party who simply wasn't in sync with the agreed upon wishes.
Some content management companies are happy to just demonetize stuff... others are cutthroat and won't let anything stay.
While it's possible to get all these things cleared up AFTER the fact - it can be very difficult to do PRIOR.. which makes live productions highly voltile.