> To be successful

Then it's a choice on the part of manufacturers, not an obligation. Look at Amazon: they decide to do without.

To be successful, you need to breathe. I will now remove all oxygen from the room. It's your choice, not an obligation, to then negotiate with me to provide oxygen. Unfortunately for you, there are no other oxygen providers to negotiate with. But you could, after all, grab some water and generate your own oxygen...

I think it's noteworthy that the only counterexample you can find is a tech behemoth with an even larger market cap than Google. If this was a person with an analogous scenario to be "successful", aka put food on the table, this would clearly be negotiating under duress.

Following that logic, it would be impossible to dominate an OS market since an OEM always would be free to write their own.

Yes, the Fire Phone was a stunning success, and clearly evidence you can compete with Google's proprietary Android offering with your own fork. /s

I would argue Kindles are largely successful because they don't compete with proprietary Android in any appreciable metric: Google-flavored Android barely even attempts to compete in the tablet market, and Kindles are e-readers first, and tablets second.