I think that's what's happening is that the big tech cos have had conversations with their lawyers along the lines of "it's one thing to host talk of insurrection from Bob in Knoxville when it looks like cosplay fantasising, but it's another to host it after they killed an on duty police officer while storming the Capitol building with intent to kill senators". The provider's potential liability in planning high crimes will tend to focus minds in a way way that "hosting deplorable speech" did not.

I'm not suggesting that the deplorable speech was mere harmless fantasising, as it seldom is, on a long-enough timeline. Just that this justification is manifestly no longer tenable.