You're correct about the control of speech. At the moment at least Twitter, Google, and Facebook are private companies, and under the law and in the eyes of the Free Market, they can choose what they want to show and what they don't. It's their product, their rules. They kept the former occupant of the oval office on their platforms for as long as it was profitable to them.

The solution entails more than questioning the philosophical idea of "Free Speech", it involves considering the nature of government and human rights in an entirely different light than the currently dominant neoliberal economic consensus.