The issue with Facebook is not that it is a monopoly. Even if it was broken into smaller business the social media piece would still be operating in violation of the 1964 Civil Rights Act.
Mark Zukerberg and the moderators of Facebook have a set of deeply held religious beliefs which are loosely known as “wokeness”. By denying access to people with different deeply held beliefs (i.e. traditional conservatives) they are violating the Civil Rights Act and should be held legally liable in court. This is also true for Google, Twitter, and any internet site that removes content or blocks users for purely ideological reasons.
It’s as if the phone company canceled service to people who talked about things Ma Bell didn’t like.