Explain Like I'm Five

Intel's big shift was to maintain compatibility as improvements were made and new fab nodes introduced. No one else did this very well. The actual baseline for this change was the 16 bit i8086 thus the reason we call it x86. A program written for an 8086 should still work on a brand new 14900 i9.

Motorola was the big backwards endian device. They did lots of odd things too, like major possessive egomaniacal like business decisions.

A couple of the key persons behind the microprocessor are Frederico Faggin (https://en.m.wikipedia.org/wiki/Federico_Faggin). He's the guy behind the Intel 4004 (first microprocessor), Intel 8080, Zilog Z80

Bill Mensch (https://en.m.wikipedia.org/w/index.php?title=Bill_Mensch) He's the guy behind the Motorola 6800 and MOS 6502

I have no idea where people are saying the 6502 has anything to do with ARM. ARM stands for Acorn RISC Machine and later Advanced RISC Machine. RISC is a fundamentally different architecture from CISC.

The 6502 wasn't really positioned in this RISC/CISC paradigm, it was simply dirt cheap when everyone else was much much more expensive. Its only real innovation was the extremely primitive pipeline where the next instruction is loaded at the same time one is executed. This is because their quality was too bad to compete with the higher frequency devices from other companies. It was a clever hack to make things cheaper at the time. The 6502 is still present in some form in Western Digital products (also Bill Mensch).

CISC was the old guard, RISC is from Berkeley, while MIPS is from Stanford. (https://en.m.wikipedia.org/wiki/Reduced_instruction_set_computer)

ARM is a RISC architecture and that traces its history back to completely different origins than the other microprocessors.

The funny thing, the Arithmetic Logic Unit (ALU= CPU secret sauce where the action happens) in modern Intel processors is a RISC design with a CISC wrapper.