It's not meaningless though. With all the checks and balances that the rust compiler enforces, you have a higher likelihood of having a correct and less buggy program.

In this context, "correct" and "less buggy" are referring specifically to memory safety issues which garbage collection can also solve. Sure, theoretically the C++ JS Engine that powers Postman could maybe have a memory issue when loading up JSON. Until that actually happens, switching to this for a subset of the tasks Postman (or the Chrome dev tools) accomplishes is a waste of time.

And community engagement compounds — people like contributing to rust projects, so we can trust the project will continue to grow, so we'll use it, so more people will contribute, etc etc.

This holds even if the original reason they enjoyed contributing isn't a good reason!