But rewriting after the exploratory phase is over (or to be more precise: long after the exploratory phase is over) is still an achievement of Rust: not only be

But rewriting after the exploratory phase is over (or to be more precise: long after the exploratory phase is over) is still an achievement of Rust: not only because it's fashionable (it sure is), but because it gives reasonable confidence that you won't find yourself regretting having rolled back multiple decades of weeding out lurking memory bugs. A C rewrite promising a moderate speedup wouldn't so much be skipped because it was not worth the effort, they are not done because the speedup isn't worth the risk of having to go through all that again.