I'm sure there is a potential in the scandinavian routes, but at the moment
they don't seem to be doing great.
Apart from a low cost alternative for Helsinki, the great thing about Norwegian is that it is no longer confined to Scandinavian routes.
There are bases at LPA/TFS/MAD and BCN?. They also offer Malaga to MUC/CGN so, the scope widens. Also a potential site for a base. Yes, some routes already have a lot of traffic, but many routes do not (MAD/LPA/TFS/VIE/IBZ), and lets face it, with their OTP and things like wifi, it would offer a competitive edge to some carriers.
It also offers seats for TUI, so, another potential source of passengers on any MAN-Sun route.