That's probably the moment they could face regulation. Individually, it's their platform to choose what they want to host or not.
The former guy got banned on all the services all at once. Even tiktok which he was not on. Hell, even grindr banned him.
There may not be direct coordination (maybe there is), but there's a signal and no one likes to make waves
They all took a different direction about the "pee tape":
https://www.nytimes.com/2018/04/16/opinion/comey-book-steele...
https://www.nytimes.com/2018/10/30/magazine/nothing-proves-y...
https://www.nytimes.com/2021/05/15/business/media/spooked-pr...
For more: https://www.google.com/search?q=site%3Anytimes.com+trump+pee...
https://en.wikipedia.org/wiki/Biden%E2%80%93Ukraine_conspira...
The complaint seems to be that the corruption he was probably involved in is slightly different than the corruption Trump was talking about. Which again, standard political fare but the crackdown on the story seems suspicious. If it had been Trump there is no way such a story would have been quietened down.
[0] https://en.wikipedia.org/wiki/Hunter_Biden#Investor_and_lobb...