On the history of Valve and Linux: Valve and Linux have a symbiotic relationship today, but they go way back, and their story is a long and interesting one.

I feel like an important piece of the story regarding how directx changed game development is that it was Gabe Newell, a microsoft employee at the time, that led the DOOM95 porting project which cemented windows as the gaming OS .
It feels poetic that Steam was part of getting Vulkan and Proton off the ground.