The big "enabler" was their mass-purchase of 5nm lithography across the board. Even still though, 4ghz*8c isn't anything new, and isn't really that remarkable besides the low TDP (which is incidentally dwarfed by the display, which draws up to 5x more power than the CPU does). I think the big issue is that Apple has painted themselves into a corner here: ARM won't play nice with the larger CPUs they want to make, and the pressure for them to provide a competent graphics solution on custom silicon is mounting. They spent a lot of time this generation marketing their "energy efficiency" and battery life, but many consumers/professionals (myself included) don't really care about either of these things.
"the display, which draws up to 5x more power than the CPU does" - wat? Apple-supplied monitoring tools report that M1 under full load (all CPU and GPU cores) can draw over 30 watts. Laptop displays don't consume 150 watts. If anything, the displays in either of the M1 portables likely consume about 5 times less than 30W, even at full brightness.
"ARM won't play nice with the larger CPUs they want to make" - wat? Apple holds an architectural license. This means they paid a lot upfront a long time ago and therefore have a more or less perpetual right to design their own Arm cores without input from Arm.
"a competent graphics solution" - Also wat? M1 has an excellent GPU. It doesn't compete with discrete GPUs that use 300 watts, but that's fine: M1 is the chip for entry level Macs, designed for the smallest and lightest segments of their notebook line. And in that product segment, it has been every bit as much a revelation as the CPU. It's very fast, and uses little power given the performance.
What exactly do you think is going to happen when they scale that basic GPU design up? Despite your dismissiveness, in modern silicon architecture energy efficiency is incredibly important: for any given power budget, the more efficient you are the more performance you can deliver. The performance Apple gets out of about 10W on M1 suggests they'll have few problems building a larger GPU to compete with Nvidia and AMD discrete GPUs.
