never said sith didnt rule galaxy at 1 point.
I am going to go very far with this answer. Because of this alternate universe in my mind (thinking 3k years ahead) Vader finds Luke as a teenage kills Owen and Beru and trains Luke to be a Dark Lord of Sith to take down Palps just like Vader wanted.
even though this game will NEVER make it that far (mybe 1.5k years of content before people get tired) I like hte idea of Luke going to the darkside. but that is also derailing the topic so I will stop there.