Why does the Steam Deck run Linux? Blame Windows
The Steam Deck and the software inside of it are the culmination of a nearly decade-long hedging strategy embarked upon by Valve chief Gabe Newell and company many moons ago, when Microsoft tried exerting more control over developers with Windows 8.
Source: Why does the Steam Deck run Linux? Blame Windows - PCWorld
Proton is pretty amazing, especially if you don’t want to buy a Windows license, like me.