This chart was made by ousted homophobe Br*ndan E*ch who clearly has a particular axe to grind, and the right side of its Y axis is a normalized value for some reason, but its point stands.
I wouldn't call it them "doing" Rust in that they don't have any exclusive control of it, just being (major, I think) contributors. But I'm not really familiar with this so perhaps my perspective is wrong.
Unlike Firefox, Rust would continue on quite well without Mozilla but I doubt that Servo and the other web rendering projects under that umbrella would survive. I'd expect most people working directly on Rust itself at Mozilla would be able to continue doing that elsewhere.
Since they've integrated Rust components into Firefox, I can't them dropping their investment into it anymore. Previously, it was quite feasible that they'd wrap up Servo and cut it loose. They can't abandon it as low-hanging fruit during these kinds of layoffs anymore though.
It was already restructured in a way that it's not really a Mozilla project anymore. Members of the different teams can leave Mozilla (including being laid off) without losing their positions. It's defacto controlled by Mozilla employees but not really Mozilla itself anymore.