> Rust was used primarily for rewriting things (compared to, for example, Go, which was used to write new things, not replacements

How could you possibly know this, for either languages?

FWIW, I've only worked and written greenfield software with Rust, and have only worked professionally with Golang to replace existing services. I'm sure I'm not alone in this, nor in the complete opposite. But I don't think either of us could say how either of the languages or "primarily used", that's a bit too much.