The DOJ should really be looking at things like YouTube, which doesn't make any profit (I don't believe) but since Google proper supports it, no one can compete with it. That might be why Google is pushing so hard against ad blockers, they need to make YouTube profitable to avoid prosecution.
You could innovate and make a better product and it doesn't matter because you can't outbid Google.
I doubt that the same number of people willingly choose Google, otherwise they wouldn't be paying so much money to be the default. That's a lot of money to throw away.
Outsourcing arrangements many different motivations, it’s not just money. Otherwise, basically any outsourcing arrangement can be said to be “throwing away money” for one party.
For everyone with Windows, you start off with Edge/IE and then Bing as a default search engine. Yet, most switch to Chrome + Google almost instantly. People care about their browsing experience more than we give them credit for. Remember in 2009-10 when Chrome was new, it managed to win market share cos of superior product when it was not the default on Windows/Linux/MacOSX. On mobile too, the behavior is likely going to be there to a certain degree. While Google pays Apple a massive fee, there was an admission earlier in the trial that both Mozilla and Apple would still go ahead w Google (even without the deals) because of superior UX. Not sure if both said it, but one of them certainly did.
[1] https://danariely.com/the-power-of-defaults-in-how-we-eat/