Allegedly Google pays between $8 billion and $12 billion each year to be default search engine on Iphones and Ipads[1]. They could stop paying Apple and save $12 billion every year.
My only reasoning is if Google doesn't pay some other search engine will for example Bing but then again Google is the most searched word on Bing[2].
So Google is entrapped in a situation where they are afraid not to be default search engine on Apple devices because Microsoft could jump in or even Apple itself with its future search engine. I don't see how this decision is reasonable because let's say Google pays $100bn in 10 years that's a lot of money that could've been invested elsewhere or even in Google Search itself.
This brings me to conclusion that Peter Thiel was right when he said Google bets that no one else will come with better search technology so Google uses its enormous cash flow to stay dominant instead of investing all that cash to improve search technology and and come up with search innovations[3].
[1] https://www.cnbc.com/2020/10/21/apple-services-success-story-bolstered-by-huge-google-payments.html
[2] https://www.bbc.com/news/technology-58749525
[3] https://www.youtube.com/watch?v=2Q26XIKtwXQ
Once you detect there's a problem it can be very difficult to stop the spread.
Let's say Google did stop paying Apple. Initially there would likely be no change. If and when there's an issue, whether that's from Bing or Apple launching their own service, presumably it has too much mindshare for people to go back to Google, and that point a crack in Google's search dominance has be made.
Then it's just a matter of money to carve out a significant niche.
Better to just pay up front and ensure that doesn't even happen.
That search service could then spread beyond the iPhone, into Google's territory.