Yeah, like others are saying, this is not a game with a typical "victory." It has an "ending," of course, when the timeline ends, or when your dynasty dies, but the game itself has no pre-set goal. The goal is whatever you decide it to be. Essentially it is a simulator, and you are "winning" if you are having fun playing it.
This is what I've found out. Sense the show vikings is my inspiration, I'm playing as Alfred. So far I have Mercia, Angela and Wessex. Currently I'm trying to decide to either go for Gweynny to bolster my forces, or attack Jorvik.
I became king of England and Ireland. Stood my ground against multiple northern armies. Became a saint. Finally just died once Alfred reached 70 years old. RIP Alfred.