The only angle I see is that it's likely to get some extra TV coverage here in the US. Ireland is 5 hours ahead of Eastern Time, so it's close enough to run the event live (6pm Ireland = 1pm ET / 10am PT) and not have to broadcast it in the dead of night.
Guessing that by having a Week Zero game coupled with an international broadcast will probably help secure us a prime ESPN or ABC time slot and get more national exposure.
But that's literally the only thing I can think of. It's not like we're playing Notre Dame in Ireland. The Illini don't have any visible connections to Ireland either, but I suppose swapping them out for the Purple Nerds means all the Micks and Murphys will be rooting for the coach named Patrick Fitzgerald. The only way Fitz gets more Irish is if he moons lights as the Lucky Charms mascot.