Most YouTube takedowns are not done through DMCA. They're done because YouTube cooperates directly with many content owners to do takedowns voluntarily. There are almost no legal limits or regulatory terms to what YouTube is permitted to voluntarily take down.

Fair Use is only a legal defense. It is not a requirement that YouTube host your content.

YouTube does not employ judges or humans in deciding whether to honor a content owner's request. It doesn't employ anything. It is up to the content owner to police themselves, only when they mess up royally will YouTube remove them from the content owner system.

Tom Scott has a great video on Copyright:

https://www.youtube.com/watch?v=1Jwo5qc78QU

That made me laugh. Because my movies were also taken down because of background music. And that was the feeling I got when I raised "dispute" in YouTube system to defend my videos. It was like a Russian roulette