I feel like attributing this to Valve is really disrespectful to the folks who developed wine for decades

Honestly, it feels like comments like this are just intentionally missing the big picture, or just don't understand any of what Valve actually do.

It's been said by comments elsewhere, but Wine was really not good years ago. It was difficult to use, obscure as you had to seek it out and know what to do. Valve funded DXVK, VKD3D-Proton, various extra Wine patches and pushed it all together into Proton with Q&A testing, regular upgrades for big games to get them working ASAP and put it in front of millions easily directly in the Steam client.

and more recently also Vulkan

Which once again, Valve massively helped push and even hosted the early discussions on it.