How was the prosperous Kattegat not taken over in Vikings?

Question

I love the Vikings show on the History Channel and I am a huge history buff but I am having some major major issues with several plot points this season. I am more than willing to give artistic liberties to the show but I need someone to give me a viable explanation for a few things.

The first is how the hell has Kattegat become some major hub in the area, King Ragnar is MIA, Queen Aslaug (does nothing but sit pretty and have sex with "gods") at the helm, Ragnar's boys being very very young at the beginning, and the city having so much wealth from past raids equal no one wants to take them over?

How would a city with little defenses not have a new king in the 10+ years Ragnar was gone?

Seriously it could be anyone but during last season Halfdan sure seemed to insinuate that he wanted to take Ragnar's seat. So he hears of Ragnar disappearing and just does nothing? What am I missing here?

Answer 1

King Finehair and Bjorn. That's what you're missing.

King Finehair wishes to destroy the Lothbrok dinasty, but he cannot do it unless he takes the throne from Ragnar. Now, when Ragnar died killed by King Aele, that's a different reason. But back then it seemed to me like King Finehair was still an ally of Kattegat, if not Ragnar's ally.

And Bjorn had already some reputation. He grew as a leader strong character since the bear and Paris. And everyone looked at him as the son of Ragnar Lothbrok, the first man to raid west. Even so King Ragnar was gone, his name carried weight. Add that to fact of Bjorn protection and King Finehair allience, and done. No one would dare to attack Kattegat.