When CPUs ran at 10 or 20 megahertz it wasnt too easy to do other things than the tasks at hand.
Ruuning at 5 giga hertz and how many dozens of tasks at the same time, its so easy to hide bad code and backdoors galore.
Nobody really knows what their machine is doing anymore.
I saw a PDP-8 with 8K of memory accurately simulate a lunar landing by the LEM. I bet nobody could do that now.