Using your activity as a substrate for ads has always been Google's business model, and never been a secret. You don't have to go along with it, but it's not a revelation.
The revelation was that Google Maps was no longer just being used to collect data, but was being used to actively push ads outside of Maps itself. That was a bridge too far for me.
In the time since, I have rid my device of all Google applications, as Google's overall model is not something I can tolerate any more.