Obito planned to lose to Minato all along. He needed someone special( a child of prophesy) to control the Kuubi so than in the end, he could use that person(Naruto). He somehow planned for Oro to use the reaper unseal. He planned it so that when Naruto takes Dark Kurama , he becomes momentarily corrupted the Yin's evil. He must have known that there was a precise moment during the fusion of both kuramas that makes Naruto mentally weak, via the corruption. But the whole point was to make Naruto seceptable to genjutsu. During that moment, he gives use a very special Genjutsu to make Naruto experience all the negative emotions/suffering felt by everyone on the battlefield. And it also makes him see the ugly side of humankind. Naruto, angry and pissed at how terrible the world is, then turns to the dark side... Obito needed to do this since he knows that his body is imperfect and can't hold the Juubi for long. So the actual eventual Juubi Jin was Naruto all along, the prophesied child, the mirror reflection of Obito himself. Only Naruto can understand Obito well enough to create a Genjutsu of his liking.
That would be a nice twist.
That would be a nice twist.