Almost all company-sponsored programming languages are run as loss leaders to enable selling some other profitable product of the company. What is the profitable product that Rust enables?
Well an IDE would’ve been one option, as well as backend services for enterprise who are migrating to Rust. Otherwise as I mentioned the product is services like outsourced development, consultancy and training resources?
People used to build a lot of software around Gecko, there are still some notable users like Komodo IDE, but Firefox is a lot harder to embed than it once was. Servo from the Rust team was supposed to solve this by providing a new embeddable browser core, not sure if that is still the long term plan
Firefox apparently is not longer a focus because it is hard to monetize outside of the search box, see earlier letter. I would definitely not take Firefox' future for granted at this point.
Firefox is the only thing Mozilla has ever been able to make any money with; anything else has gotten them a pittance at best.
Giving up on that because it's 'too hard', without first proving they have an alternative? That would be insanely foolish. They may as well close up shop now if that's their plan.