The foundation is about 80 folks on payroll, although OSS projects have about 1000 contributors popping in and out.
There is also the “MZLA Technologies” subsidiary, which I think has some dedicated headcount under it as well. Although, there isn’t a lot of public info about that company.
Maybe I should’ve said “midsize.”
My point is that they’re not a company with tens or hundreds of thousands of employees. And, as someone that usually likes to work at companies that are about size, you can run out of engineers pretty quickly if you’re not focused and or working on stuff that is wickedly complex. And Mozilla is definitely doing the latter.