How many people do you think a browser's team + all components + support + management + marketing + finances need? Chromium alone has 1700+ contributors (https://github.com/chromium/chromium), Firefox has hundreds of "core contributors" (https://wiki.mozilla.org/Community#Core_Contributor) and many more beyond those.

It fell victim to the same problem as Wikimedia, a kind of Dutch Disease: The web browser was too good, they earned so much money in donations from it that it attracted freeloading middle managers and do-gooders who don't give a flying f about the browser, but started empire-building with vague new "missions".

Not really. It's an organization dedicated to promoting lofty ideals for the Internet as a whole. It was pretty cool while it lasted.

Besides trying to prevent the Web not to turn into ChromeOS (before it was WinOS), top quality browser engines don't get coded during weekends.

The bulk of open-source code is written by employees of corporations.