One can only speculate for the reason why they "refused", I would chose to use the word "declined" instead.
They probably got to see some of their books and saw that what ever the airline is saying is not deemed to be realistic.
Edit:
At this point in time it is a overstatement to say that Norwegian is critical to the Norwegian infrastructure. That argument is not valid.
They have SAS (who is being held under the arms by the Swedish and Danish state, and partly by subsidised routes in Norway)
Wideroe, and now also Wizz Air to keep the prices down. Oh, and a new start up with one of the Braathens family members.
Why would they dump money into Norwegian?