For user land it doesn't matter at all as people can mix and match whatever languages they want as long as there is an ELF entry point into the runtime. However rewriting the kernel, which is what this discussion is about, is a whole other matter.
But as bawolff said, the main issue is moving towards safer tech. If Ada had good enough momentum, we'd be discussing Ada in the kernel instead. C++ has been rejected from Linux, leaving Rust as the only kernel-capable language with enough momentum, so Rust it is.
That has nothing to do with memory safety though let alone Rust specifically. What we need is a smarter way to manage authentication (non-persistent session cookies and usage a password manager to handle the log in is a step in the right direction).