Opinions aside, that’s still not the legal definition of a monopoly.
Monopoly: Exclusive control by one group of the means of producing or selling a commodity or service.
Valve does not have exclusive control of the PC gaming market. The EGS funded lawsuit even says that in the docket. They are only suing on the grounds of the keys issue. I don’t disagree with you that when Newell leaves, things COULD change, but you can’t base the present on the possible future. At this time, steam is on “top” because the vast majority of users have voted with their wallet and time. Not because they are engaged in sweeping anti-competitive backdoor dealings. You know, like EGS does.
The difference is he was a poor trying to pull himself up. Corporations are glorious entities that can do no wrong in American law.