It seems a bit ridiculous to call a multi-year investigation by the EU's anti-trust agency "calling in my friends", but ok.
The most severe thing they did was give retailers a hard choice: Either they only sell phones with Google's Android distribution (AOSP+Google Play) or they only sell phones with no-name AOSP distributions. They cannot sell both.
As missing out on the revenue from Google Play-based phones would be financially irresponsible, this choice had only one viable option: Not selling any other AOSP-based OS except Google's.
Therefore Google effectively made competing AOSP-based projects extremely hard to sell, regardless of their quality.
