There was never any real commitment to the "best" search engine in a region. Mozilla has been paid by Google to be the default search since 2004.
I also think I remember Firefox’s default search engine in Japan regularly being used as an example of doing right by users.
I am 100% sure it has. But the point is that all search engines are willing to create these funding deals, so that leaves the freedom to pick the ones that you think are best for users.
But the whole point is that Mozilla is trying to have revenue, obviously, but maximizing it is not a goal, as long as it covers expenses.