It’s a matter of priorities. A large portion of Linux users don’t actually care about adoption. They’re not selling the os, so the docs aren’t designed for anyone who isn’t already a user.
Valve on the other hand is paying people for documentation and good ux. That’s enough to significantly boost the quality.
It’s even still a valid course of action if there’s literally no interest in making the world better.
They’ve potentially found a way to make their nearly omnipresent e-commerce platform share a name with the operating system, which is coincidentally mostly developed by others. They get to associate their name with a few tens of billions of dollars of development effort for a fraction of the cost.
To be clear, this isn’t bad or anything. It’s quite literally what a lot of the people doing all that legwork want. It just doesn’t require any altruism from valve. They make money selling games, and they sell more games when people think it’s easier to play them. A desktop with the ease of a console is a big selling point for a lot of people.
I think they gave it two wireless adapters for basically that purpose. That way it and the computer can form a dedicated channel where they don’t need an intermediary for better performance.