For the fiscal year 2022 which is the most recent data on Wikipedia, it says that 81% of Mozilla's revenue is from Google (about 480 million) they list 220 million as expenses for software development.
If they lost the Google revenue they wouldn't just have to fire "the C suite" but lay off most of their engineers. An independent browser engine is a project with code in the tens of millions of lines, you obviously need to pay hundreds or of engineers to work on this, which is why there's pretty much only three competitive ones, all maintained with significant resources.
It's a large code base, but it doesn't require hundreds of developers working concurrently to keep it up to date. Web standards move fast, but not that fast.
Take a look at Ladybird. There's a browser being built from scratch with a small team (less than 10?)
If Mozilla fired 90% of it's employees and kept the 10% to actually work on Firefox, it could be a great browser.
Have you taken a look at Firefox's bug bug tracker?[1] Keeping up with Web standards is nothing compared to the tremendous amount of work required to maintain a cross-platform web browser.
If they lost the Google revenue they wouldn't just have to fire "the C suite" but lay off most of their engineers. An independent browser engine is a project with code in the tens of millions of lines, you obviously need to pay hundreds or of engineers to work on this, which is why there's pretty much only three competitive ones, all maintained with significant resources.
https://en.wikipedia.org/wiki/Mozilla_Corporation#Finances