Except Ireland joined the EU and with the agreed to the fair and equitable taxation policies. Simply said the agreement is to tax all businesses alike within your borders. The idea is to promote free trade by preventing state aid. So for example the Irish government cannot give a construction company(A) special tax rate that would be lower than that of another construction company(B) as this would give (A) an economic advantage allowing them to submit lower bids for work than (B). So to ensure a level playing field for all you must treat companies equitably, so corporation tax is a flat rate on profits for the small corner shop to the large multinational.

The money would go to the Irish Government, which isn't some African corruption ridden state, so it would have gone on improving things in Ireland.

For example it costs approx €1bn a year to maintain their water supply. As an austerity measure they have had to recently introduce specific water rates rather than cover it from general taxation. This tax bill (if paid at the time it was properly incurred) could have prevented the need for that for a decade or more, and at a time when there was an economic crisis it would have meant consumers having more money available. Instead it can now only be used by the Irish government to pay off their deficit, which is a long term benefit to the Irish people.