Would that have been profitable for them in all cases? If it wasn't, then they didn't.
it's not just the effort of "step up", which I have seen on social media. It's the effort to suppress disinformation, which although we have seen some, a lot more gets through. I haven't seen much antivax stuff, but that's because the algorithms know me. You have to understand how much of the "on social media" experience is tailored to you, and how much YMMV. And how it's driven by engagement for profit, not by "stepping up" to do the right thing.
e.g. Youtube radicalisation:
https://www.nytimes.com/interactive/2019/06/08/technology/yo...
https://theconversation.com/youtubes-algorithms-might-radica...
Likely based on their past browsing experience ?