How do you reconcile your claim with the fact that Yandex has been the default search engine in the Russian localization of Firefox for years?
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.