Getting direct3d and vulkan working with actually useful performance

They definitely spent an ass-load of money on that

[citation needed]

I'm not aware of Valve or Doitsujin ever revealing how much they paid him to make DXVK. I assume they paid him reasonably well, but I doubt it was an ass-load.

the fact that Wine was around for 25 years before that just goes to show that no one else was willing to do that.

Or maybe that Wine was a lot more work than the direct3d-to-vulkan shim that was done mainly by one person (now two people).

Valve definitely helped by funding a few key projects, and packaging them in Steam made them convenient to use, but I think exaggerating their role unfairly diminishes the much larger body of work (done by other people) that makes it possible at all.

Proton stands on the shoulders of giants.

I mostly agree with your comment, but...

the fact that Wine was around for 25 years before that just goes to show that no one else was willing to do that.

Remember that Wine is built by community of volunteers (afaik, tell me if I'm wrong), and they don't have as much resources as company worth billions USD.

direct3d Direct3D 11 and Direct3D12, to be precise. Direct3D9 was working fine before - and there even was native driver support for it in Mesa, that could be used together with a patched WINE.