Have you seen benchmarks post 1st page? M1 at 7-8W power drain beats or just trails behind a desktop class $799 Ryzen 9 5950x at +49W consumption in single threaded performance. What did you expect?
The 5950X's uncore consumes a significant amount of power, but penalizing it for that seems more than a little unreasonable. The M1 is getting power wins from avoiding the need for externalized IO for GPU or DRAM, but those aren't strictly speaking advantages either. I, for one, will gladly pay 20w of power to have expandable RAM & PCI-E slots in a device the size of the Mac Mini much less anything larger. In a laptop of course that doesn't make as much sense, but in a laptop the Ryzen's uncore also isn't 20w (see the also excellent power efficiency of the 4800U and 4900HS)
But you cannot extrapolate these numbers (to multi-core performance or to more cores or to a possible M2 with a larger TDP envelope), nor can you even directly compare them. The Ryzen 9 5950x makes an entirely different trade-off with regard to number of cores per CPU, supported memory, etc., which allows for more cores, more memory, more everything...and that comes at a cost in terms of die space as well as power consumption. If AMD had designed this CPU to be much more constrained in those dimensions and thus much more similar to what the M1 offers, they would surely have been able to considerably drive down power consumption - in fact, their smaller units 4800U and 4900HS which were also benchmarked and which offer really good multithreading performance for their power envelope, even better than the M1, clearly demonstrate this fact.
What I read out of these benchmark numbers is: the ISA does matter far less than most people seem to assume. ARM is no magic sauce in terms of performance at all - instead, it's "magic legal sauce", because it allows anyone (here: Apple; over there: Amazon) to construct their own high-end CPUs with industry-leading performance, which the x86 instruction set cannot do due to its licensing constraints.
Both ISAs, x86_64 and ARM, apparently allow well-funded companies with the necessary top talent to build CPUs that max out whatever performance you can get out of the currently available lithography processes and out of the current state of the art in CPU design.
This was my conclusion too. Does this mean, there is not much possibility of desktop pcs moving to ARM anytime soon? Perhaps, laptops might move to ARM processors, but even that seems iffy, if AMD can come up with more efficient processors (and Intel too with its Lakefield hybrid cpu)