In fairness, that's nothing to do with the Premiership; that was always the case, even back in the day when LoI teams had respectable attendances. Phil Lynott was a Man Utd fan, for example. Irish players going abroad to the big English clubs ensured an extra interest in that club here.
Gods versus Mortals highlights that point very well, I think.
Try
handball, skiing and ice hockey for starters. Norway's similar. The notion that Ireland is unique in having the GAA as a competing sport is just wrong.