I think the fourth is quite a few people spotted what appeared to be happening in big tech, where if you have the right activists in only a few companies you could cover and (to some extent) control a lot of digit communication. The moment whatever issue du jour came up that they did not align with the big tech decision on, they noticed and started to distrust what they were seeing. It's possible that being a benevolent gatekeeper only works if you are extremely nonpartisan.