That was Saxons, not Scandenavians
Virtually the same religion. When the Saxons did not convert just because a missionary told 'em to, Charlemagne put 'em to the sword and trashed their holy places. Many Saxons hightailed it to Scandinavia as a result. Also, Charlemagne was warring with the Danes at the time, and many Norwegians were on his side... but they turned against him when he intentionally targetted the Irminsul (in 772), an oak pillar of religious significance. (As the crucifix is the symbol of Christianity, the World Tree was likely the binding symbol of the old Saxon/Norse faith.)
Widukind was a Saxon leader in the fight agaisnt Charlemagne; when Charlemagne beat the Saxons in 777, he went to Denmark. He eventually converted to Christianity in 785, but that left quite a number of years for he and those who went with him, or just those who had also been driven towards Scandinavia due to Charlemagne, to tell the tales of what happens if you don't stand up for your beliefs. There is an aggressive alien religion coming at you from the South. They do not play well with others. They will convert you or kill you or live in a state of war with you. They will trash your holy places. What will you do?
Hmmmm... parallels, parallels...