The Communications Decency Act (CDA) Section 230 was enacted in 1996 with the main purpose to protect interactive computer service providers that offer a family-friendly internet experience from certain claims of third parties.
Big Tech Platforms that harm their customers by removing or misdirecting content that the customer wanted to receive, or not attempting to deliver the content that the customer have sent, are not protected by the Section 230.
In interactive services, any transaction (a message, post, tweet, video, etc.) has at least two parties other than the service provider: a sender and a receiver. At that time, the service provider usually had no contractual relationship with at least one of those parties in the transaction.
For example, ISPs had contracts with their subscribers but not with the websites that their subscribers browsed. When an ISP, acting on behalf of its subscriber, blocked a porno page on a third-party website, the website owner could potentially sue the ISP for wrongful interference with a business relationship. CDA 230(c)(2) protects the ISP from such liability. CDA 230(c)(1) protects service providers from claims of defamation and similar torts, made by third parties.
A provider of a bulletin board could not know people who used it — much less have a contract with any of them. There was no need for such contracts. There was no certainty that a contract could be made electronically until 2000, when the United States Congress passed 15 U.S. Code Chapter 96 – ELECTRONIC SIGNATURES IN GLOBAL AND NATIONAL COMMERCE.
Today’s Big Tech social media platforms (and search engines) do have or claim to have contracts with their consumers, including those who do not have accounts (so-called browse wrap contracts). Although these platforms’ terms of service, user agreements, and sundry policies are void or even illegal, there are actual contracts that can be construed by courts based on the platforms’ promises and reasonable consumer expectations from those promises and other platforms’ conduct. However, CDA 230 provides no protections to the platforms against their users when there are contracts, attempts to bind users by a contract, and/or promises made by the platform to its users.
P.S.: Section 230 was somewhat influenced by Stratton Oakmont v. Prodigy (1995). Prodigy acted as an early internet service provider (ISP) and operated moderated bulletin boards. Because of this moderation or because its earlier statements that it operated as a publisher, the court found Prodigy to be a publisher of these boards, liable for defamatory statements posted by anonymous users. By the way, allegedly defamatory statements were found out truthful.
 Section 230 was only a small part of the CDA, which was struck by the Supreme Court. Only Section 230 has survived; it is discussed in legal proceedings as if it was passed independently.