Kingdom Hearts has always been popular. Discussion on it just died down when the series went portable.
Remember that we have Tyler Posey (Teen Wolf), Nina Dobrev (Vampire Diaries), Katherine McNamara (Shadow Hunters), and more playing the game in 2013, and those people were on long-lasting television shows with big audiences.
Because the series is back in the lime light, and it has now evolved to meet the gaming standards and futures of today, more celebrities are showing off their excitement for it. Plus it gives Disney a chance to promote the game to other audiences, like with the Thirteen Reasons Why fans at E3.