A big part of it is that Apple literally places the memory on the same package. It’s literally inside the black package that has the CPU, GPU, and some other dedicated processing units. This system-in-a-package configuration allows the M series chips to have memory bandwidth that basically no other system can match.
Intel tried to put memory on package, but has announced that it won’t be doing that anymore, probably because it’s so expensive to do so.
Even some of Intel’s Arrow Lake/Lunar Lake chips are being fabbed at TSMC.