You can thank "The Shannon Lobby" and the parish pump nature of Irish politics for the resultant situation of Dublin boasting the shortest main runway at the major airport of any western European capital city.
Back in the days of the stop over, there was no reason to extend (despite plenty of room at the 10 threshold end) and the pressure on then Aer Rianta to keep it that way via government was significant. All fine and well when going west required a stop in Co. Clare. Pretty dumb today when all the new business opportunities are a way off to the east.
JAS