If you consider the big-budget courses constructed in Ireland in the last 25 years, the majority of them have been designed by well known architects from abroad. Developers have not been willing to take risks with lesser known architects.
The American market is very important to the Irish golf industry, so it was a natural choice for many of these developers to choose American architects such as RTJ Snr. (Ballybunion New, Adare Manor), Nicklaus (Mount Juliet), Palmer (K-Club, Tralee), O'Meara (Carton). Nicklaus was also involved in the re-development of St. Patrick's in Donegal. It's important that the architect is well known and Irish developers have only considered the signature names up to now. I don't see that changing.
In recent years, we've seen non-American architects getting a bigger slice of the pie, with Norman (Doonbeg), Montgomerie (Carton), Eby (US) with Langer (Portmarnock Links), Faldo (Lough Erne), etc. getting a look in.
Pat Ruddy and Christy O'Connor have been quite prolific in the last 20 years, working on jobs at existing golf clubs, or smaller scale developments.
I'm pretty sure an architect as talented as Eddie Hackett wasn't seriously considered for any of these big projects in the 80s and 90s. Hackett even advised a developer to seek a big name, rather than choose himself, if the developer wanted to guarantee commercial success.