Comment by mike_hearn

KMP can call into native libraries easily. C FFI is not a competitive advantage.

Rust has a smaller library ecosystem, I'd say. Kotlin can use Java libraries on the server side, and on the client side on Android, and the ones needed on iOS are easy to convert to KMP - IntelliJ can do it semi-automatically. And KMP has the libraries that matter on mobile, for hardware access, animations and so on.