Do you know what the big difference for companies to cram enough hardware into the same space to support 20W power like Anker [1] Is this just incremental improvements or is there a technological breakthrough that's enabled this?
There's a slow transition underway from Si to SiC power-semiconductors in industries such as automotive.
You can relive my emotions from when I learned about the astounding properties of nitride transistors (in 02017, I think) in https://dercuano.github.io/notes/jellybeans.html#addtoc_1. Unfortunately there weren't any carborundum parts in my list.
SiC has significantly higher thermal conduction than both Si or GaN, though, which makes it more suitable for cases where you need a ton of thermal capacity (inverters for EVs, for instance).
Both technologies are in their infancy, though. You can get better performance out of either by improving the process technology aspect, so it's hard to say one will ultimately be better than the other. Given the electron mobility though, it seems GaN will ultimately win for devices that aren't thermally limited.
But similar logic applies even for the ones that aren't using GaN. More efficient parts and/or designs allowing for more and more shrinkage. One of the other big drivers has been manufacturers starting to market monolithic chips that manage all the aspects of power regulation and USB-PD in a single/small number of parts.