The thing is, historically, Ireland isn't very politically or culturally inviting to a large Jewish settlement in the first place.
I'm not talking about Anti-Semitism exactly, it's simply that for most of it's history, the only cities in Ireland large enough by any stretch of the imagination to support a Jewish Quarter are Dublin, Belfast, Galway, and just maybe Cork. While a review of the legal history of the island before Stonebow doesn't show any legal barriers to rural Jewish legal tenure (Recalling that from the establishment of the Merovingian Kingdom until the rise of Hugh Capet, French Jews were prominent vintenors), Brehon Law imposed a rather harsher form of serfdom than most of France until the Angevin period that probably would be rather less than appealing. And joining the Travellers would mean the same social friction with the peasants that Jews would have wanted to get away from back on the Continent in the first place.