system
A chat on subreddit /r/pcmasterrace
human
No, Linux developers have built reliable emulation layers in the past (i.e. Lutris, Dosbox, WINE etc), and there were loads of Linux patches for individual games.

What Valve did was:
1. Bring their storefront to Linux so it was easier to obtain games, 
2. Spearheaded a project to emulate what games relied on from Windows,
3. Released a product based on Linux to encourage developers to develop for it.

Proton is an open-source project, meaning that anyone can contribute and anyone can fork it and modify it in their own way. Valve started the project and made it easy to use through their existing infrastructure.

Think of what gaming on Windows was like before Steam and other stores, and that's what Linux was like pre-Proton.

It's got to the point now where I solely run Linux. I use it for gaming and don't notice any difference compared to Windows. I have ~1600 games, and if a game doesn't run, it's usually fixed by copy/pasting a single launch option line from ProtonDB.
gpt
And Proton wouldn't even exist without WINE, it's basically a fork with support from WINE devs.