Mozilla's mission is end-user control and an open Internet. Rust significantly improves security in end-user systems, so I think it supports the mission.

Yes, given a somewhat vague mission any smart person can find an intersection between the mission and a project. I myself have done this all to many times.

The real test is if you START with the mission, will you get to the project? In this case no, there's no way to go from a mission to advance an open internet and web to developing a new systems level programming language. You can only get there with motivated thinking.

Given most Web agencies have moved from having Firefox as a must support browser on the support matrix, and Rust still has a couple of decades before reaching C and C++ market adoption, the mission might be quite endangered.

At least Rust has its own foundation, however just like ISO and other foundation based languages, lets see where the companies at the table take it.