Sometimes doing things because they are hard is a great reason to do them to see if the reasons those things are hard are still valid. Doing a filesystem in Rust potentially mitigates some of those things. Most existing filesystems have gone through a lengthy stabilization phase where using them meant exposing yourself to nasty data corruption bugs, obscure race issues, and other issues that, when you root cause them, have a lot to do with the kinds of things Rust explicitly addresses (memory safety, safe concurrency, etc.). So there's a great argument to just try to leverage those features to make things easier and try to build an awesome file system.

Worst case this doesn't work. Best case, this works amazingly well. I think there's some valid reason for optimism here give other hard things that Rust has been used for in the past few years.