Oh, that's easy: I was there. I was in meetings about strategy now and then. I certainly don't claim to know everything (I worked outside android team but helped it. I received the same awards/etc the team got), but I know enough.

Now, you can certainly choose not to believe me. But I can state for sure the main intent of the people building and running android was to build a great mobile experience for users. When I say "nobody was thinking about ads". I don't mean "nobody considered the possibilities". I mean: Nobody saw it as a goal. It was not driving the decision making process. In fact, some people saw it as an anti-goal.