Google paying Apple massive amounts of money to keep Google Search the default search engine on their devices doesn't seem to be affected by the fact that Pixel phones (or Android as a whole) and iPhones are competing. Though I gotta admit that it could be because Google doesn't have the overwhelming winner position in that market, as opposed to the web browser market.

However, I still find Google pulling the funding unlikely, given (afaik) the reason for Google "financially supporting" Mozilla is exactly because Google is afraid of being legally called out as a monopoly in the web browser market. The only point at which I can see Google pulling that funding is if Mozilla ends up on the same level as Chrome in terms of posing a danger to Google's dominance. At which point, Mozilla has already won and doesn't need Google that much to sustain itself, so I wouldn't pose it as a strong concern.

But if they can garner 5% market share via this new approach then they save themselves from destruction long term.