Why can’t Cork Airport swing PSO grants?

Newspapers are reporting how the Minister for the Gaeltacht, Heather Humphreys was present at the inaugural twice-daily Donegal to Dublin flight, which is to be operated by Aer Lingus Regional (Stobart Airlines, previously Aer Arann).

Cork has no flights to Dublin, whatsoever, the alleged reason being that it is not cost effective.

So how can Donegal (county population of 161,137) have such a flight when Cork (county population of 518,128) can’t?