Innovation in heat-sink design?
My consumer level desktop computers mostly have pump/heat exchangers on the CPU with a separate radiator and a couple large fans mounted on the case, with fluid-filled tubes between.
My notebook computer has heat pipes running from certain chips to a heat exchanger and small fan.
The science of getting heat from a small area to the room air has not really changed in 20 or 200 years, but there have been a few incremental improvements that allow 50 to 200 W generated in a few square cm (a square inch or so) of area to be moved out to the room air without adding too much weight or volume.
In the 1960s we would probably have  used a kg or so of aluminum and a large fan or water cooling to get hundreds of watts out of a big hockey-puck thyristor.
Heat pipes have been around for more than 60 years, fans, radiators and electric pumps as well, but many of those things were too expensive for consumer use. Mass production and Asian manufacturing has led to (at one time unimaginably) cheap, light and good fans, pumps, heat pipes etc.