The "free" part in free software is not just free in beer, it's also free in freedom. That little bit gets forgotten. People work on it because they want to, not because they have to. If a developer does not want to use Rust, they can and should not be forced to. It does not matter if Rust is objectively safer, or better, or any of the purported arguments. Forcing it eliminates the freedom of choice.
The Rust folks should make their own kernel and OS. Let it compete directly with Linux. In open source, this is the way.