I believe Amazon uses CryEngine for Lumberyard. Amazon must have given them a deal so bad that they end up bankrupt if the software isn't adopted.
More cynically, it's a deal structured to ruin them and make them cheaper to acquire. I don't think that's the case though.
The AAA scene is using their own engines or the unreal engine. While you can switch engines when creating a new game the incentive isn't there when you either already have licenses for the unreal engine and a small army of programmers who have mastered it.
People were expecting a shit to Unreal when they decided to make it free for education/take a 5 % cut. This shift hasn't happened...
https://steamdb.info/app/252850/graphs/
The game was free until November 18th 9am PST, so the current active ~100 daily players is more representative of its success.