[ineptech]

Without a harmonized tax, Ireland could also lose all of its corporate tax receipts to some other country that's willing to stoop even lower.

More generally, this is a variant of a mutual coordination problem in game theory, in which it is everyone's interest for everyone to cooperate, but in each individual's interest to be the only party that doesn't cooperate. Those are notoriously tricky to induce/enforce agreement on, but it has been done.