How are Apple and Google and Amazon telling Parler that they are liable for any speech on their platform, but at the same time advocating for their own Section

How are Apple and Google and Amazon telling Parler that they are liable for any speech on their platform, but at the same time advocating for their own Section 230 protections? I’m seriously asking, I don’t get it. Is there a better answer than “it’s their app stores they can do what they want!”? Because Parler exists because someone didn’t like Twitter and was told “if you don’t like it build your own”. Also, how are these companies acting in concert not a violation of coercion or antitrust laws?