I can recommend the book “Androids” for an in-depth look at the origins of Android and the team that built it:

https://www.amazon.com/Androids-Built-Android-Operating-Syst...

The definition of a phone OS was very different in 2005 when Google acquired Android Inc.

It was a tight platform originally, but so was Windows NT, and look at Windows today… That’s just the nature of success in the open OS space when you’re serving lots of hardware vendors.