Steam

Second, Valve argues that the plausibility of Consumer Plaintiffs’ claims hinge on allegations that Valve acquired Sierra’s World Opponent Network (“WON”), which Valve contests with a single affidavit. That argument fails for multiple reasons. The Court must reject Valve’s extrinsic evidence, which is contrary to its public admissions, at this stage. Regardless, the Complaint does not turn on these allegations. Valve’s relationship with WON, whether by acquisition or otherwise, helps explain how Valve has had monopoly power in digital PC game distribution since the beginning. But it is not the only relevant fact. Independent of WON, Valve leveraged its enormous installed user base and popular PC game franchises to force gamers onto Steam, such that when Valve began selling third-party games in 2005, it already held a monopolist position.

From the document you linked.