Collusion implies coordinating on something illegal or worth hiding from the public - what exactly is the alleged wrongdoing? That Twitter had people that work

Collusion implies coordinating on something illegal or worth hiding from the public - what exactly is the alleged wrongdoing? That Twitter had people that worked with both presidential campaigns to expedite the review of moderation requests? I mean, by this definition, what interaction between private institutions and politicians doesn't qualify as collusion? Like what principles are even being violated here?