Re: Naruto Manga Chapter 594 Discussion and 595 Predictions
Let's assume for a second Tobi WAS Izuna. If he told Sasuke that he willingly gave his eyes to his brother and why he did it, your question then becomes trivial. We know that Itachi wasn't there when Izuna 'lost' his eyes to Madara, and we know that a lot of things Itachi told Sasuke were to instill hatred into him so he would seek more power. There are plenty of reasons to believe Tobi's account over Itachi's, especially if he were actually there (because he's Izuna).
For what purpose would Izuna want world peace? Plus we don't know if it's true that Izuna willingly gave up his eyes and is now working together with Madara. Itachi said that they were forcefully taken, and Tobi has been known to lie before. The whole theory of Tobi being Izuna is hinging on that one little fact.
I'm not confused at all about the timeline. You have to understand that Kagami was the same age as Danzou, Hiruzen, and the elders who were on their squad. That time frame was when Tobirama was second Hokage after the battle between Madara and Hashirama took place. At the time of that Battle, Madara was clearly working with someone else to carry out some sort of plan.
It's not impossible that Kagami could have been there to do all those things. Remember that Kagami would have been around his late 40s early 50s (around Hiruzen's age) when Nagato was given the Rinnegan. Kagami DOES fit because he's old enough to fit. Nagato was born years AFTER Tobirama died not before. Your times are mixed up. Kagami is an old man now, just like Tobi.
"There's also a window of time around the battle between Hashirama and Madara, where SOMEONE had to be helping him" -- This is complete speculation. There is no reason to suggest that Madara had help in his fight, besides Izuna was presumed dead after he lost his eyes.
After all, why would Madara just throw himself into a battle against Hashirama just to die? And yes, Izuna could have died like Tobi says, or it could have been a figurative death. With everything we know about Madara, Izuna, the Uchiha clan, and Konoha, Izuna is the one person who has the most motive and opportunity to be Tobi.