Google regained control of Android many years ago by progressively moving every bit that matters from AOSP to Google Apps and Google Play Services.
Now OEM have to obey to Google because losing the Google apps and services licence (thus losing the Play store and the whole ecosystem) basically means they're dead as an Android manufacturer.
Now OEM have to obey to Google because losing the Google apps and services licence (thus losing the Play store and the whole ecosystem) basically means they're dead as an Android manufacturer.