Shannon does not have a larger hinterland in terms of population as Cork Airport does. Nearly 500,000 in Cork County alone not including most of Kerry, large parts of Tipperary and Waterford where Cork Airport is more easily accessible than Shannon. All of Clare, Limerick, North Tipp would only account for a pop of around 350,000 add in Galway and it gets to 575,000 still less than Cork Airports hinterland.
In terms of companies unfortunately Limerick/Shannon region has one major multi national dominating employment and that is Dell. Cork fortunately has a broader spread with more companies therefore more business travel.
So in terms of air transport in and out of the South of the country Cork ticks more boxes for airlines wanting to do business, it also has not put all of its eggs in one basket (eg Ryan air sweet heart deals ****ing off the competition).
Also Shannon has been seen by other regions as having had its own way for far too long in terms of unfair advantages over other regions eg the Shannon Free Duty zone and the Shannon stop over so the plight of Shannon Airport is never going to get that much sympathy from other regions.
Maybe Cork is next, I don't know but it has survived far worse.