It’s described in detail at Anandtech [1][2]. It has mostly to do with the fact that Apple’s chips are so much larger in every way measurable. There’s no magic, just raw performance from comparably massively over engineered designs. At the time of its release their reorder buffer had 630 entries vs Intel’s 352 and AMD’s 256. The floating point units inside the cores could handle quadruple of Intel’s throughput per clock. Etc. Etc.

[1]: https://www.anandtech.com/show/16226/apple-silicon-m1-a14-de...

[2]: https://www.anandtech.com/show/16192/the-iphone-12-review/2