Simplicity is one of the main virtues of engineering. To solve a complex problem (version control) in a simple way that works (git) is a major feat of (software) engineering.
Domain knowledge, or the genius to reinvent it from scratch (CAS and merkle trees for Git)
"heroic" is ill-defined, so don't know about that, but the effort was arguably extreme, in the sense that Linux and git are among the best at what they do. Lots of other people who might have the same experience and abilities did not achieve things like that. I just don't see why you would want to minimize the achievement in any way.