Do you realize what 1.300.000.000$ is? Say you invest most of it in a safe way to get you inflation + 2%. That gives you 26.000.000$ every year. You can pay 100 engineers with this. Firefox is a browser. Sure a browser is complicated but 100 motivated and talented engineers is more than enough to make a good product if you focus on what matters.
There is no excuse to what is going on.
I dont even think they employ close to 100 FTE devs actually working on Firefox at this point.
How do you think they got that money in the first place? They've been growing this fund from $100MM in the 2010s to where it is now, by carefully managing and investing it.
Hilariously, you're here presenting something Mozilla has already been doing for nearly two decades like it's a new idea that only you have thought of. Yes, I realize how much that is: enough to cover their operating costs for like 2.5 years.
And sure, it's amazing how much an endowment can do if you give up and wipe out most of their staff and embrace magical thinking.