For anyone who knows.
Basically, it seems to me like the technology in mobile GPUs is crazier than desktop/laptop GPUs. Desktop GPUs obviously can do things better graphically, but not by enough that it seems to need to be 100x bigger than a mobile GPU. And top end mobile GPUs actually perform quite admirably when it comes to graphics and power.
So, considering that, why are desktop GPUs so huge and power hungry in comparison to mobile GPUs?
I just want to add, the Nvidia 4090 mobile gpu is the 4080 desktop chip, but at lower clocks and therefor better power efficiency. However it has much lower performance in comparison to a desktop 4090 and lower than the desktop 4080 as well.