[GianFabien]

Obviously the persons mentioned had considerable knowledge to start with. But the key to their accomplishments is that they built something then iterated on it.

For example initial work on Linux was based on Minix and then refined and evolved on the basis of experience. 30+ years later Linux is still being developed, refined, evolving as hardware platforms change, bugs fixed, new drivers added, etc. By Linus's original announcement, Linux started out as a tinkerer's prototype. There was no grand plan to start with. More like curiosity and wanting to address a personal itch.

As an engineer you learn by doing. Experience is the best teacher.