Nerd sites were screaming about it, extensions existed to remove them, for the reasons you say. The web devs generally knew this was an issue but the clicks were more important. I don't pity them.
Ignorance is no excuse. Don't dump loads of third-party JS onto your site without understanding what it does. That's negligence.
If Facebook misrepresented what the code (or whatever) Patreon included was going to do, sure, ok, fair. But then in that case Facebook should be the target of the suit. (Unclear who should sue whom, though... users sue Patreon and Patreon sues Facebook? Users sue Facebook directly?)
> JS onto your site without understanding what it does. That's negligence
Everybody understood what it did. It was legal at the time. Then it was made illegal. The lawsuit literally retroactively includes the period in which it was legal.