Something similar happened in the past where Google blocked Microsoft's YouTube app on Windows Phone.

The reason was that the only official way Google allowed for non iOS/Android clients was if they used the HTMl API. Microsoft decided they wanted native performance so they wrote their own client to YouTube instead of using the HTML API. Microsoft's YouTube didn't play advertisements, which obviously Google wasn't ok with. So after some back and forth Google just said "No".

I think Amazon probably made a similar mistake here.