[color=#2e1a6b]When people die while possessing a tool or ability (such as Zabuza's sword), they retain it when they are revived by edo tensei. For example, Itachi had his Sharingan when he was revived because he died while having the Sharingan, even though his eye's were transplanted into Sasuke. Madara had the rinnegan when he was revived, which means that he must have had the Rinnegan when he died. Nagato had the rinnegan during the 2nd Shinobi war, which means that Madara must have died during/before the 2nd Shinobi war. After Madara died,
Tobi took Madara's Rinnegan and gave it to Nagato. Both Tobi and the revived Madara have implied a plan to use Nagato's Rinne Tensei to revive Madara.
Tobi also implied that Madara's body was inaccessible.
Simply put, Obito could not have done everything that Tobi has done, unless Obito was Tobi before he got crushed in the cave.
Zetsu's ability to become an identical clone of someone could explain all this.