I think you're right that Apple needed an overlap period, but I also think doing that would have been very difficult. Google certainly wouldn't have been happy

I think you're right that Apple needed an overlap period, but I also think doing that would have been very difficult. Google certainly wouldn't have been happy with a public beta of a replacement app. Meanwhile, Apple wouldn't have wanted Google to launch their own future app on the App Store in the interim. Could those have been the sticking points in their negotiations?