Exactly how is it much better? It's not the first chip with a 15-25W TDP. When compared to other chips with such a TDP, it's incrementally faster in single core and it trades blows in multicore. It does this at a process node ahead.

For very light loads, it does have a slightly better power performance than existing low power PC processors, but not by that much. A Ryzen LPP core is somewhere between the big and the small cores of the M1 in power performance in such cases.

It's not the first PC chip to be an SOC, or to have unified memory, or to have many coprocessors. Literally all of those were done simultaneously, in chips of comparable performance, at the same power.

It's also been a decade that we know that instruction sets don't matter. All modern PC processors use a different instruction set and translate from x86. To switch them to ARM would be a matter of adding a few extensions to expose all the functionality, and change the instruction translation stage a bit.