I honestly don't know why Google keeps funding Mozilla. Maybe it's a "useful fool" type of situation where having an inferior browser they can financially puppeteer helps them set their own standards (via WHATWG), since Firefox tries to keep parity with Chrome. Having another browser toe that line maybe helps legitimize those standards such that Google can remain in control and not worry as much about W3C/Microsoft/Apple domination? I dunno. Just speculating here.

It matters less these days since Microsoft gave up and went Chromium and Apple just doesn't care about its browser. Maybe Google already won and Firefox is on its last breaths?