People seem to misunderstand generally the concept of "competition".
Look at the competition for say the Marathon race. Wha happens at the end of the competition ? There is a winner. Right. And likewise in a commercial competition where the "best" may prevail, this does not mean there will be a constant steady state of equals. There will be a winner.
The Irish market is not a large one in the general scale of things. It's a small country, only 4.5 million population. Not one to sustain two large carriers long term. It is inevitable that one will eventually dominate over the other.
It's the same in the US, competition has meant that in all but a couple of hub cities, one carrier comes out on top after competition, is dominant, and then charges higher fares than in a freely competitive market. That's how an unregulated market goes.