Gish gallop of post-hoc nonsense. This is how things are - so it must be the only way it’d happen.
Market share is literally the only factor in what defines a monopoly. But people can’t even bring themselves to say they have a monopoly, even as they defend that monopoly, because that sounds bad and Steam good therefore nuh uh. Let’s go round and round and insist that buying games online in 1999 didn’t exist, and then Steam happened, so literally everything since then is thanks to Valve. Nothing else changed! No outside factors!
All of the things I’m talking about are hard prerequisites to those markets existing at all, they’re things no one else ever tried to do, and they’re things that PC gaming would be in far worse shape if someone like Epic had done first, because unlike Steam, it’s a literal certainty that they’d abuse them.