Keep listening, because some of this is mentioned in the show. ;) But here's a short summary of my thoughts…You have the "wandering of the peoples" thanks to the Huns and others, so things on the continent weren't stable or safe for a bit. And then later on you have signs of climate change, and the people of the Danish peninsula probably needed to get out of there. But where could you go? You can't go south, the Franks were just too strong. So the obvious choice is to go to the fertile island where other Germanic settlers had already moved to in the fifth century (and were probably doing pretty well).