NCL always had plenty of need for these flights. very big N.Irish community, quite sizeable community from the republic, although spread out over the region. 3 universities, 2 of which particularly attract overseas students, lots of employees on the rigs, increased business and if you go abroad, all you hear is that NCL is the new Dublin/barcelona/amsterdam/prague. Particularly peeved in DUB, since that place is sooooo expensive. I've twice in the past year seen travel articles relating to city breaks in NCl, one french the other spanish. I'm not surprised it's taken off, add to the that the aforementioned lcc 'creating' need, you've got a very full airport.
An example is the fr offer of '1,000,000 free seats' at the mo. I went on the website and decided that with my 2 days off in early june, i'm off to ancona..never ever wanted to go there, but it's 20 quid and a quick trip to the appeninos never hurt anybody.