I think it's less about safe, and more about Rust's other qualities. The language lends itself to writing parsers thanks to its syntax and zero-cost abstractions. Match expressions in particular made parsing a breeze when I last dabbled in writing compilers. The way it makes you think about memory management saves allocations you'd accidentally make in languages with GC. And it probably doesn't hurt that rust/cargo are nice tools that guide developers onto writing similar CLI experiences.

In short, it shines for this problem domain in my experience.