I see people in this comment section posting alternatives to Youtube but I really wonder if, should they become equally as successful, they could end up behaving any different.
When you get thousands of videos uploaded at any given moment and probably a huge amount of DMCA takedown requests what choice do you reasonably have? If there's one thing Google doesn't want is to be sued by the copyright owners, so they always take the defensive stance of taking the content down until proven innocent, which seems cynically reasonable to me.
That guy makes song covers. He claims it's non-profit, he claims it's fair use. The IP owner disagrees, issues a takedown. At this point Google either takes the content down, or starts a lengthy and risky legal battle on behalf of third party content that they do not control. I can't really blame them for not bothering.
BTW, IANAL and all that but I'm not entirely convinced that his "non-profit fair-use" defense would even hold up in court. Surely he monetizes his videos on top of asking for donations and putting ads on his website. Given his number of subscribers he probably makes a significant amount of money from these videos.
To be clear, I think ethically what he does is perfectly fine, but as we all know IP laws have very little to do with ethics. Focusing on big bad google is a bit simplistic here IMO.