They were "known" in the same sense that everybody already "knew" that the US government spies on us before Snowden leaked the details.
Twitter claimed that they didn't shadowban - in fact there's a tweet out there somewhere (I think I saw it shared in one of the Twitter Files threads itself) in which Jack Dorsey himself explicitly denies that Twitter shadowbans. To claim that the Files didn't reveal any new information is utterly disingenuous.
Interesting how you moved on from “government involvement” when everyone realizes Biden campaign wasn’t the government and it was dick picks they were trying to remove.
Shadowban was literally talked about earlier this year. https://www.theverge.com/2022/4/5/23012046/twitter-prisoner-...