It feels a little like when Microsoft invested in Apple back in the 90s. Microsoft needed Apple so they didn’t look like too much of a monopoly. Google has been funding Mozilla’s whole existence for at least 20 years. At first it may have purely been do dominate search, but at some point I think the incentives shifted to Google needing Firefox so they can claim they aren’t a monopoly in the browser space and competition exists.
And anyway you're factually wrong. They produce much more than what you listed, many of their undertakings are contributions to open-source, the development of web standards, underlying technologies that browsers (not just Firefox) use to render the web, etc.
You're being childish and somewhat absurdly so. Mozilla and Firefox are a large part of the reason the modern web is usable (in the technical sense - usability for the deaf and blind, screen readers, etc)