But Mozilla trusts Google more than any search engine provider. That would be the only explanation for Google being the default search engine.
the bills don't pay themselves you know
The real explanation doesn't have anything to do with trust: Google pays Mozilla a lot of money to be the default search engine on Firefox. Deals like that are Mozilla's main source of revenue.
https://www.zdnet.com/article/googles-back-its-firefoxs-defa...
I'm not really sure why you're viewing this as the end of the world, especially since all the money that Google pays to Mozilla enables the development of Firefox in the first place.
What else are you gonna use? lynx?