At the very least, it was collusion by these entities to shut down a competitor. Obviously, Trump and his White House didn't make this move, but it not beyond the real of possibility that this current White House would coordinate with these companies if they wanted to.
And as far as we know (just speculating), there very well could have been some behind the scenes conversations between the incoming administration and these social media companies. Promises made on future legislation or as you brought up... maybe some exchange of money???