Their very first examples are Engineers with formal training. Formal training gives you the mathematical and engineering maturity TO tinker.
I was doing some embedded stuff when i was at school. I needed to run some "functions" in parallel. Obvious choice would be using a RTOS, but i did not know the exist of RTOS, so i spun up some timer interrupt, a "queue" of function to run parallel, an isr that acts like "scheduler", some variables that act like "semaphore", etc.
Only few years later i realized i have invented a very simple "RTOS"
Back in 1955, "computer science" wasn't a thing yet. Computers were the domain of electrical engineering and math, the latter of which was what Margaret studied..