There is a long history but the short of it is, before Section 230, platforms that moderated user content faced potential liability. Oakmont v. Prodigy[1] is a case where Prodigy was held liable for defamatory posts due to its moderation efforts. However, in Cubby v. CompuServe[2], the court ruled that platforms without active moderation, CompuServe were not liable for user-generated content because they were just hosting with no active involvement. Section 230 protected platforms from liability for user content, allowing them to moderate in good faith without being held responsible for all harmful material if they weren't able to moderate everything.
I believe Elon and Trump, being the internet's biggest liars, have the goal to remove Section 230 making moderating online more or less a crime that will open you to litigation and allow them and all of their followers to spread lies not only unchecked but with the threat of punishment if a company, like Blue Sky, were to try to moderate them.
I wouldn't mourn the loss of BlueSky, because it's basically designed from the ground up to create filter bubbles and echo chambers, and social media needs way less of those.
