A lot of responses and none of them are false but the main reason for the improved gaming performance is DXVK, it translates DirectX 9 and 11 to Vulkan and is used by default on every DX9/DX11 game on Linux when you use Proton.
The Vulkan stack on modern GPUs is much more optimized compared to DX9 and 11. It has gotten so bad that many Windows people use DXVK on Windows to solve performance issues and even Intel uses DXVK (or similar technology) for their Arc GPUs.
A lot of responses and none of them are false but the main reason for the improved gaming performance is DXVK, it translates DirectX 9 and 11 to Vulkan and is used by default on every DX9/DX11 game on Linux when you use Proton.
The Vulkan stack on modern GPUs is much more optimized compared to DX9 and 11. It has gotten so bad that many Windows people use DXVK on Windows to solve performance issues and even Intel uses DXVK (or similar technology) for their Arc GPUs.