Apple definitely makes a lot of money from advertising...probably more than they make from selling Macs (based on 2022 results).
Also I think this quote might be technically right, but Mozilla's revenue is almost entirely paid from advertising companies who pay royalties to have their search engines by default in Firefox. So they are very much coupled to the dynamics of the ads industry.
Not doubting you, but do you have a source for that? Best I could find was their last quarterly earnings report which does have “Services” ahead of everything but iPhone, but I would imagine includes some big money makers like AppleCare.
Just a small correction. Large parts of revenue are obtained though sharing ad revenue between Mozilla and a search engine, not for being the default search engine.
Also I think this quote might be technically right, but Mozilla's revenue is almost entirely paid from advertising companies who pay royalties to have their search engines by default in Firefox. So they are very much coupled to the dynamics of the ads industry.