I read an interesting story, that claimed that Christianity, not fighting skills, saved England from the Vikings. The religion of the Vikings was extremely harsh, and probably one of the only religions ever created where the gods themselves die. This is not a very uplifting or positive message. The Vikings “conquered”, and then settled down in northern England, married, converted, and generally assimilated.
There is likely at least some truth to that, but remember that the Vikings grew tired of raiding just what are now the Baltic States and were sending raiding ships as far south as Sicily and North Africa. The French gave them Normandy in return for stopping the raids on Paris, converting to Christianity and learning French. So there was a lot of contemporary exposure to Christianity in about the same era as their raids on England.