Valve has been investing in Linux gaming for nearly a decade now (to my knowledge), and it's looking like a really good decision. I've recently set up new Windows and Mac devices and it's just glaringly obvious how tightly they're clamping down on their respective platforms. My perspective is a that of a Linux sysadmin who hadn't done a fresh Windows install in over a decade, and took about 3 years off of using Apple products.
It's definitely an arms race, and the experience is getting worse and worse for customers (including software developers). I don't know if the average user notices these things or not. Valve is trying to not get caught in the crossfire here, and to have some recourse when inevitably MS wants 30% to allow steam to run natively in Windows. In the meantime they also have built a strong reputation among nerds like us, mostly as a byproduct.
The grandparent is saying that Steam didn't want to have to run on Windows, so they're investing in Linux so they can use that as the base OS for gaming. Otherwise Microsoft could demand a cut.
