Earlier quoted context omitted.
As far as I know, covers aren't fair use. https://www.legalzoom.com/articles/posting-cover-songs-on-yo... Thousands (millions?) of people post covers on YouTube with no issue, but sometimes people get unlucky. I don't think monetization makes a difference in the eyes of the law (maybe it would for proving damages? I'm not a lawyer.) What's unusual is that he said he got 5 copyright strikes without telling him why. I'…
Covers might not be fair use, but teaching is. https://www.copyright.gov/title17/92chap1.html#107
Funny enough, they cite a case where a content creator (h3h3 productions) was able to prove fair use in court as an example of the system working. If you look into that case though you'll see that the claimant was only an individual musician and not a big studio, and even then the legal fees were hundreds of thousands of dollars.