This isn't a mystery. Mozilla accept donations. It isn't an ordinary for-profit corporation.
Yes, they separate Mozilla Corporation from Mozilla Foundation, but the point stands. If Mozilla are going to claim to make browsers, apps, code and tools that put people before profit, [0] they should expect backlash when they lay off engineers while continuing to overpay their leadership, despite continuing poor outcomes under their stewardship. [1]
Some people have an axe to grind with Mozilla since that whole Brendan Eich thing, and on top of that there's just good old sexism.
This all contributes to create a very toxic subject that I generally tend to avoid, but I think that it's fair at this point to question Mozilla's execs results at this point. These past few years have been pretty brutal for Mozilla, and there's no clear path ahead from where I stand.