I think the end of season 3 has explained all plot holes and flaws that we spotted from season 1 to 3. If Magne has written the story himself - considering his state of mind and trauma since his present in Edda.. it was understandable that the story would be like this.. From the conclusion, I think that we can not count on the version of reality or events that we have seen throughout the 3 seasons.
It is also understandable that many viewers and fans do not like the ending and explain it differently.