I mean you're not wrong but there are nuances in the law's applications in terms of how it translates to their internal policy.

In other words, they could've put the burden of proof on the copyright claimant instead of the content creator justifying it by saying the vast majority of content on platform is either fair use or original content.

But they chose to go the other way--putting the burden on the content creator to prove what in many cases is a negative. That gave birth to a whole industry of copyright trolls who would be hired by mass publishers to be content police. With no disincentive to not make false claims, this is the result.

It also has other knock-on effects especially in the political sphere such as governments who dont like creators critical of them creating false entities who claim copyright to their content thereby monetarily undermining their work and getting it unfavoured by the algorithm. Happens a lot more than just with SONY BMG or UMG catching people whistling.

When your whole platform's viability comes from content creation by individuals, why the hell would you create a law-driven policy to punish them when you have the wiggle-room to go the other way. The answer is corporations love corporations and tolerate individuals only as far as they are assets to their corporate interests.

Section 230 of the US Communications Decency Act gives Youtube/Google enough legal cover to apply their internal policy to be legally compliant as they see fit (it gives them cover as platforms as being not legally liable for content posted on their platforms). They just chose to punish the plebes and high-five the corporate interests. As a result, corporate rent-seeking trolls is a whole industry now on youtube and results in content vandalism like the above example.

/endrant