They read each-other's press releases, they reasearch competitors, employees and mamagers move between companies. There is no way for them to not communicate.

Just because bosses didnt sit down a and sign a deal in a smokey room doesnt mean no decision was made

Yes, although typically tacit collusion is introduced with the example of price matching at big box retailers. The setup in this case is somewhat different, although the outcome is still an equilibrium in which all sellers "agree" to keep prices high (and above marginal cost) without directly communicating.

Steam has a much better case to argue, given that they're a fiscally independent company with no board of directors or shareholders to satisfy. Since they don't get monthly cash infusions, they need to do two things: shoot for an aggressive growth model, and shower the end user in features. In my opinion, they've succeeded in both regards: their 30% cut is pretty large, but it's justified given the scale of the operation they run. Plus, their generosity with things like cloud save, video streaming, and their assortment of community offerings, it's hard to really claim that Steam doesn't deserve their cut. If anything, I consider them the premier example of what a "premium" CDN pipeline looks like.