In the case of Elden Ring, not really, it was due to DXVK (whose developer is sponsored by Valve) having custom patches to workaround the weird DirectX streaming logic of the game that caused constant frame hiccups.

So, on day 3 or something of release, Linux was the best platform to play the newest AAA game.

The year of Linux gaming has been here for a while.

It usually has to do with a translation layer, converting DirectX to Vulkan (there are a few different ones, depending on the version of DirectX).

And yes, gaming on Linux has been infinitely smoother and gets leaps of improvements every year. We're at a point where unreleased games already play on Linux, and typically with better performance than naively on Windows.

Controllers, audio, etc, all play out of the box, perfectly, since years now