While executives earn money like at any company, most of their budget is spent on Firefox. 2% of the Mozilla Corporation revenue goes back to the Mozilla Foundation.
That downplays the remuneration of the principle Moz exec considerably AIUI. Mitchell Baker's remuneration from Moz was >$2M last I heard (a few years back [see eg https://calpaterson.com/mozilla.html]), I can only assume it's more now.
There was also a report Baker had a >$1M "stipend" (uncharitably a bung) from Google, though I've been unable to refute/corroborate it.
The last report is from 2017 I believe, a year when Mozilla's revenue hit an all time high $562 million. I personally doubt her salary is as high, despite her promotion and I believe the overall decrease in amount of executives that accompanied it.
Seriously, "Chair pay is .5% of revenue" seems fair.
And I haven't heard this "bung" rumor but Mozilla's revenue and usage were shrinking long before Baker became CEO in late 2019.
Personally I find the idea of a charity begging for cash whilst simultaneously paying outrageously large amounts of money to execs to be immoral.
My limit on reasonable salary is 5 times the UK median graduate salary.
If ".5% of revenue is reasonable" surely there's no excuse not to increase salaries of everyone working for a company -- pay everyone ludicrous sums as each salary is small!
IIRC studies have shown exec salary doesn't correlate with increased company success, why should revenue come into it.
The Mozilla Corporation isn't a charity, none of the donated money goes towards their salary. And their revenue is directly tied to a specific deal that the executives negotiated to get over $100 million per year more than their previous deal. They negotiated that despite the years of decreasing users your link showed.
As for the rest, I also dislike standard corporate practices but Mozilla is more or less forced to follow them to compete at all in this world.