Given that Norway doesn't have the sort of system where you can call it a life sentence, even if everyone knows it pretty much is, I'm not sure what you expect them to do? Should a country change its laws based on the actions of one man, or should they deal with that one man in a manner that's effectively and practically the same but without having to alter their laws? I know which option I'd choose.

If he'd done what he did in the United States or in many other countries of course the result would be different. But he didn't, he did it in Norway, and Norway has dealt with it under their own established rules in a manner that works for them. I'm not sure why people are so confused by that.