Me either so take this with a pinch of salt.

Mostly it's about shuttling around 4 times as much memory for each screen as well as 4 times as much processing.

1920x1080 has ~ 2 million pixels. 3840x2160 has ~ 8 million pixels.

Internally iirc this is often done as vectors before been rasterised out and having various filters and shaders applied but that step requires that you store multiple buffers etc, same reason a card that will play a game just comfortably at 1024x768 will run away crying at 1920x1080 I guess.

I can see how higher resolutions will require the GPU to have more memory or more FLOPS or both. I guess my question is, how, if at all, are the improvements required to support 4K different from improvements that target something like deep learning performance?