Supposedly it is not in alignment with the Trusted News Initiative (TNI) [1] or so people say. No idea if that is the real reason.

[Edit] In this case I am thinking maybe Forbes had exclusive coverage and the other videos were pulled down for not having the rights to coverage. Just guessing because their upload is 3 days old.

[1] - https://www.bbc.com/mediacentre/2020/trusted-news-initiative...

It depends on what you believe the purpose of YouTube is. Just because it's congressional testimony that doesn't mean it's actually credible or vetted information. We have elected officials in the US regularly spouting absolute nonsense, so it's not implausible that the same people would also bring witnesses in to spout the same absolute nonsense, whether it's vaccines causing autism or something else.

Well, they recently did this too: https://news.ycombinator.com/item?id=27646686

I don't know if it's following their policies to the legal letter or if there's something else going on, but it's clearly bad in both of these cases.