(and no, msdos doesn't run on most 8bits. The Intel 8080 was 8bit. The Z80 expanded on that with additional instructions, and cp/m lives in this branch of the family tree. The 8086 gained 16bit instructions, and branches off in an entirely different direction birthing the x86 family tree, which is where you'll find msdos & most variants)
I find CP/M interesting because it's provably the minimum viable product for an operating system. It was the personal computer desktop operating system that really worked. It came with full documentation, a full development systems (an assembler and a debugger), and a full set of tooling to allow you to port CP/M to new systems. It was portable, too, and you could run the same program unmodified on nearly any hardware which supported CP/M. So it was this great open-ended system, cheap enough to get into the hands of ordinary people, simple enough that you could understand it all, and yet sophisticated enough that, with enough time, you could achieve _anything_ on it...
The CP/M kernel is 3.5kB of 8080 machine code. I think each frame of that video consumed more space than that.