It's easy, people don't like getting politics shoved in their faces when they're using some product that has nothing to do with poltiics. Especially when they disagree with the message.
Of course, in the Mozilla case it's more than their pander to wokeness that made them become unrelevant. It's their focus on shitty products that no one asked for or wanted. For example, Pocket. Such a waste of money, I'm sure they have some users and so on but come on.
There is no way of donating to the development of Firefox. You can only donate to Mozilla and the money won't be used for development but rather for pushing woke politics.
They have used a lot of money afaik on that purpose alone. To be more inclusive, which basically translates to excluding white men (because that is what it's always about).
But if you want some concrete list, check this one out:
https://www.oneangrygamer.net/get-woke-go-broke-the-master-l...
I'm sure Brendan wouldn't have spent millions on shit products and woke politics but rather to have improved on the core products and stuff like privacy which people actually care about.
This is why Brave will be bigger than Firefox in the long run, because they care about what actually matters. Which is the product they offer.