Back when iOS and iPad were eating Microsoft's lunch in mobile, Microsoft freaked out and released Windows 8 with that new tiles UI framework ("desktop and tablet are going to converge so we need to dumb down the interface") and the Windows Store that was supposed to be their response to the App Store. Microsoft wanted all future Windows software to be released through the App Store. Of course, this was an existential threat to Valve/Steam, so Valve vociferously pushed back.

The Windows Store and its apps were so bad that Microsoft eventually scaled back their ambitions, but Valve has not forgotten.

Gabe Newell: "I think Windows 8 is a catastrophe for everyone in the PC space."

2012: https://www.pcgamer.com/gabe-newell-i-think-windows-8-is-a-c...

He made some critical comments to the media about the Windows app store and Microsoft's position of trying to turn Windows in to an iOS type situation with everything locked down. Remember that Microsoft had just released Windows RT and later Windows 10 S which could only run apps from the Windows app store.

This could have pushed Steam out of the market if it had succeeded. Valve then spent the next decade building up Linux gaming almost from scratch to reduce their dependance on Microsoft.