It’s also not unprecedented in the tech world – Bell Labs, the research arm of AT&T’s greatest contributions to tech have nothing to do with telephones. Their researchers invented transistors (basis of modern computers), the C programming language (pretty much every operating system and most video games until recently were written in C), the UNIX operating system (between UNIX and its kinda-descendent Linux – a good portion of the research computers and the Internet run on these OSes), and many other technologies. So it wouldn’t be the worst legacy for Mozilla to have.
Rust, in case you’re unfamiliar, is a low-level language like C but it has safety mechanisms that should help reduce the number of bugs that can be exploited by the bad guys – at least at the operating system and driver level. Google has indicated it will begin using Rust in Android. Linus Torvalds has mentioned he’s not opposed to it in the Linux kernel. I believe I’ve also seen articles saying that Microsoft is considering using it for future versions of Windows.
I don’t think it would be a good thing for us to end up back in a place where there’s only one browser – Chromium and its clones, but if Firefox dies, at least Mozilla will have given the world Rust. (Also, Firefox was originally called Phoenix… just as it rose from Netscape’s ashes, maybe something else would rise from Firefox)