John Carmack, author of the Doom engine, is a long time Linux user and for a while the policy was to open source the idTech engines once they had moved on.
However, Doom was hugely popular on its own before this, and was actually more pivotal for making Windows a gaming platform (over DOS).
The reason it runs everywhere is a combination of it’s huge popularity, it’s (now) open source and it’s generally low system requirements.
GNOME 3 introduced the current shell paradigm where you don’t really have a start menu but a variety of searches, integrated indicators, per-app desktops with a dock etc.
Before, it was far more conventional experience like Plasma/Windows/Cinnamon are now. GNOME 2 was forked to be the MATE desktop if you want to check it out.