A few points of note.
Firstly, passenger figures were up 6% in January, which is respectable enough. UK up 7%.
Passenger Growth Continues At Cork Airport In 2017
Secondly, Norwegian have confirmed their NA bases as Stewart and Providence
Norwegian Air confirms Providence will be base for Europe flights
While Logan may have generated extra traffic, Providence is not too bad an option from Cork. It works as well as or better than Logan for some large employers around Cork (Pfizer, Boston Scientific, Dell/EMC). It has a train link into Boston. At launch, Cork is likely to be the only direct service to Ireland from Rhode Island, which has the third-highest proportion of Irish-Americans (after Massachussets and New Hampshire) of all states.
I'm not so optimistic about Stewart. Transport links from there to New York will have to be significantly improved before it becomes an easier option than traveling to Shannon/Dublin on this side of the Atlantic.