> only party holding enough data

Correct.

> objective analysis

Assumption.

For all we know, they could be making up bullshit to cover up the real reason; e.g. Disney/Marvel (a source of revenue) or the White House (with the threat of potential regulations or maybe just the political bias of YT staff) or YouTube themselves (YouTube Rewind) are very unhappy that their videos are so unpopular.

Since we can't access their data, we will never know one way or the other. We either have to trust their corporate PR, as you seem to have done, or analyze their possible motives for making a decision that is seemingly user-hostile.

"I don't know, so I will invent unfounded theories that can't be falsified" is a frankly stupid way to go through life.

You've framed a plausible hypothesis - which is the best any of us can do given a complete absence of any data - as "invent[ing] unfounded theories that can't be falsified". That's effective rhetoric, but it isn't really an argument.

Instead, "I uncritically accept corporate PR as objective analysis" is what I consider to be a stupid way to go through life.

Maybe your priors include "corporations always tell the truth", but mine don't.

That obviously doesn't mean we should accept some alternative conspiracy theory X as the truth, but it does mean we should be skeptical and open minded about other explanations, especially given the context in this particular case of: (i) zero supporting data provided by YT, (ii) a very plausible set of alternative explanations that would be political suicide for YT to publicly state, (iii) the apparent anecdotal user-hostility of this decision.

"Google is a bad faith actor, this is a PR piece, and so it is unwise to take them at face value on anything", on the other hand, is pretty reasonable.

I think there can be a difference between how people behave and what people want. Which means there is a huge difference between what people want to engage with and what they do engage with. For example, TikTok will aggressively optimize your feed based on what you watch. If you get hooked on a video which makes you angry or reactive (like a political take), TikTok will show you more of it. You end up engaging with that content despite not wanting to.

None of social media is optimized around what people like or enjoy watching. It is only optimized on one thing: engagement to drive ad revenue via addictive practices. Engagement != enjoyment. That especially includes YouTube.