Board Thread:Naruto Discussions/@comment-27296281-20180709203011/@comment-31099706-20180711005503

I think he kept Nagato as his life saver rather than Madara's. And seeing that Obito didn't think of the possibility of Black Zetsu controlling him to forcefully revive him, he may have thought that as lomg as edo Madara can't be alive, it will be Madara's own duty to protect and help Obito. Since if he is dead, then the only present user for IT will be gone and there will be no means of reviving him or Obito after that.