68k isn’t hard to understand, either. I think what helped most was that programs were small and that no tricks were necessary or even possible to be efficient

68k isn’t hard to understand, either. I think what helped most was that programs were small and that no tricks were necessary or even possible to be efficient w.r.t. cache misses. If Linux ran on some multi-gigahertz 64-bit evolution of the 6502 the instruction set would still be simple, but a few Gigabytes of 6502 code still would be a challenge to understand, more so if that 6502 were out of order, speculatively executing, multi-core, and various parts of the code were written taking that into account.