>>29668338He understood that Master Cyrus was in pursuit of fulfillment and meaning in life and that he'd finally found it. In spite of everything - what they'd all done together, their friendships and their ideals, Cyrus ultimately put that fuilfillment above everything else. And perhaps there was also a sense that he couldn't really get out of Distortion World and resignment to his fate, but the way Cyrus looks at Giratina heavily suggests that he's found a reflection of himself (who wants to create a world) in that Pokemon (who has already created a world.)
Moreover, the fact that an existing Distortion World would render his entire need to create a new world redundant.