Before 230, there had been court rulings that said if a platform moderated user supplied content they were liable for that content. Section 230 was written to reverse those rulings.
I'm not sure why, but a myth has taken hold that under 230 you have to be neutral to get the liability shield.
230 was written for a bulletin board site in '96.
Twitter and other social media behemoths still enjoy this protection.
There's been proposals to hold these behemoths accountable by taking away their liability IF they do not act neutral and meet a certain criteria (X users, X income, etc.).
Facebook can defend itself in the court of public opinion by claiming to be neutral, but when they are in fact discriminating against certain viewpoints they end up facing critisism and potential boycots for that, regardless of whether it is legal.