This sort of coordination is
exactly what free markets do. There's no conspiracy or coordination other than that. You may as well imply that there was some sort of coordination between every marketing department releasing an ad saying "In these uncertain times..." last March.
The coup failed, the dust settled, Biden will be inaugurated, and most importantly, the Democrats took control of the Senate for the next two years. Ajit Pai announced that he's dropping his plan to creatively reinterpret Section 230 because he won't get the rulemaking done in time. The consensus of the country and the world is that the far right has crossed a line, and there is significant public sentiment against the platforms that enabled them. It is suddenly no longer net profitable to keep them around. Every platform independently came to the same conclusion at the same time because they saw the same facts.