If you invent the next image format, compression scheme, encryption scheme, etc., and you write a Go library for it, then it can be used by Go programmers. If you write a C/C++ library, it can be used by any programmer (perhaps with a wrapper) on billions of devices.

Now, we add Rust to the list. You can write that library in Rust and it can be used by anyone, too. That's because there is no GC or other extraneous code, and because you can make structures with specifically-defined layout in memory.

Making a list of options go from two to three is a big deal. Especially when, a lot of the time, C++ ends up looking like C when you need to interface it with something else. So Rust is kind of like going from one to two optons.

I'm ignoring other good languages, I know, but those are often just not chosen for a variety of reasons. Rust seems to be breaking out of that trap because of a good community, a few nice features, the fact that it's new, and a bit of luck.