This was a question that brought a visitor to my blog today.
Of course, there are several answers, all of which are common knowledge:
1) The constant rain
2) Eight hundred years of British occupation
3) Fianna Fáil
4) The phlegmatic Celtic temperament
5) An oppressive, misogynistic, reactionary (etc. etc. etc. etc.) Catholic Church
6) Excessive expectations in the Eurovision Song Contest.
Thank you for your visit. Please come again.