Yeah, i think that's a fair question. It wouldn't be my choice, though I don't see it as like, objectively wrong. Rust gives more guarantees, for example. My guess is that it was easier to start from the existing codebase and refactor (indeed a lot of the existing codebase is still in there). But yo...

Sorry to jump in, but as any bald long-bearded coder knows, you simply don't rewrite software from scratch.