Where can Firefox generate money to fund it's development?

That's a big question for Mozilla. Because they rely on click revenue for having Google as a default search engine

Enterprises put millions of dollars into Linux because it has utility for them.

Almost nobody is doing the same for Mozilla.

Also just because someone isn't a programmer doesn't mean they are useless.

Mozilla is not just Firefox.

Also, the comparison to the Linux kernel is not a good one because there isn't a single organization that makes the kernel. These roles exist, they just are in spread out among the companies contributing to and selling Linux, and organizations like the Linux Foundation (which also doesn't just do kernel things).

Many non-profits and NGOs have huge budgets for executive compensation and perks, while they expect the people at the bottom to work for peanuts (e.g. university admins vs. lecturers).

Not saying Mozilla does this, but if your observation about their executive overhead is correct, they would not be unique among non-profits.

Mozilla just has too much money and they just can't be conservative. If all they do is build a browser and get a few docs up, which should be their core activity, they don't need $500m a year.

Why should executives have programming experience?