There is zero chance they all independently came to the same conclusion at the exact same time. There has to be a bare minimum amount of coordination involved, which is likely illegal. Either that or they got an order from the SEC/White House.
Financial companies all use the same logic to make these sorts of decisions, so yes, there is a very good chance that they independently came to the same conclusion at the same time.
It’s also not a clear conclusion even remotely at all. There’s nothing remotely illegal about retail investors coordinating together to profit from a short squeeze opportunity.