I think the thing you’re missing is that opensource people love rewriting libraries in their favourite languages. Especially something well defined, like tls or an xml parser. Rustls is a great example. You wont stop people making things like this. Nor should you - they’re doing it for fun!
It’s much more fun to rewrite something in a new language than maintain bindings to some external language. You could wrap a Java library with a rust crate, but it would depend on Java and rust both being installed and sane on every operating system. Maintaining something like that would be painful. Users would constantly run into problems with Java not being installed correctly on macos, or an old version of Java on Debian breaking your crate in weird ways. It’s much more pleasant to just have a rust crate that runs everywhere rust runs, where all of the dependencies are installed with cargo.
It’s much more fun to rewrite something in a new language than maintain bindings to some external language. You could wrap a Java library with a rust crate, but it would depend on Java and rust both being installed and sane on every operating system. Maintaining something like that would be painful. Users would constantly run into problems with Java not being installed correctly on macos, or an old version of Java on Debian breaking your crate in weird ways. It’s much more pleasant to just have a rust crate that runs everywhere rust runs, where all of the dependencies are installed with cargo.