St. Patrick’s Day puzzle

Michael Dirda, the Washington Post book critic and winner of the Pulitzer Prize for criticism, asks:

“How is it that this small island has produced so many great modern writers? One might even make the case that all the greatest 20th century writers in every genre were Irish: W.B. Yeats for poetry, James Joyce for the novel, Shaw, Sean O’Casey or Samuel Beckett for the drama. Lord Dunsany is probably the most sheerly influential 20th century fantasy writer. One could argue for Frank O’Connor as the best all-round short-story writer since Chekhov and Kipling, just as Flann O’Brien may be the century’s best newspaper columnist, of the sort the French call a feuilletoniste. In recent years think of such literary lights as Edna O’Brien, Seamus Heaney, Paul Muldoon, Colm Toibin, John Banville and many others.
“What accounts for such a constant flowering? Is it the Guinness? Or Catholicism?…”