The Barclays Center served a purpose for the New York Islanders. After a stay at the Nassau Coliseum was no longer tenable, former owner Charles Wang needed to find a place for his team to play. There was no question that the Isles should remain in New York. Preferably on Long Island.
The best option for them was to play in Brooklyn at the Barclays Center. While Brooklyn is still geographically on the Island, it's also not on the Island. So while away from the Island wouldn't sit well with fans, it would have to do.