Board Thread:Theories and Speculation/@comment-5413572-20151114042410/@comment-25122992-20151114120511

Nagato wasn't original owner of the Rinnegan, even if he managed to use it quite effectie, only Madara could use it at the fullest extent, that's why only he was suitable for Kaguya recreation. A quiote from the BZ: "The one, who managed to awaken the Rinnegan, are only Sage of Six Paths and Madara". So only Madara could accomplish what BZ wanted to make him accomplish.