"I especially had to take liberties with ‘Vikings’...we want people to watch it. A historical account of the Vikings would reach hundreds, occasionally thousands, of people. Here we’ve got to reach millions."

This is an abridged quote from the 'Vikings' showrunner, Michael Hirst, and I think it speaks volumes about the way in which historical accuracy is approached in this show. All things considered, what 'Vikings' offers is a fantastical, heavily stylized interpretation of real people and real events, designed to appeal to the tastes and expectations of an average TV viewer, rather than that of a well-read academic. Hirst has previously tried to defend a number of his creative decisions in producing this show by claiming that "no one knows for sure what happened in the Dark Ages", but this is somewhat of an exaggeration; the inaccuracies that can be found in 'Vikings' are present due to the freedom provided by artistic license rather than a lack of available research or contemporary evidence.

There is much, much more that could be said on this subject, but rather than listen to me go on about it, I would advise checking out the r/askhistorians FAQ section, which includes a whole segment dedicated to discussions surrounding the historical authenticity of 'Vikings'; this is probably the best place to start in answering your question.

Hope this helps!