Then you would have to ask, if people would only switch back to Google anyway, why is Google paying them currently? Depriving Apple of the incentive to develop a competing search engine good enough for people to willingly use.
Otherwise the terms of the deal are terrible for Google
It's still far easier to not install chrome than it is to install it: downloading a thing, running the downloaded thing, click through all the dialogs, ignore all of Windows's nags to stick with Edge (which is probably a greater abuse of platform control than advertising on the search page), ...