I agree that most of their money comes from Google (at least for now).

But when you load their home page (https://www.mozillafoundation.org), the first thing you are greeted with is a banner that says they have raised over $6M in their last campaign alone.

So, it seems that millions are being donated by users.

The claim that most of those users want it to go to their browser is not supported or refuted by that page, but I have read a detailed breakdown of all their donations and attempts to guess what people really think they are donating for, and it matched my original statement - though I haven't got the time to search now, what do _you_ think people are donating for?