Why is the SO6P trying to destroy the world, then?
Well, so6p believed in the ultimate peace of the earth. I think he never really died, but identifying himself so no one would know who he was.
I think he saw all the wars, and hating in the world, something he did not like. I think after he had seen war in many years, he decided to do what he wanted; Fix the moon eye plan.
I think it was him, so6p (Tobi) receiving Madara to get EMS, and I think that he used Madara just like he is using sasuke now.
In addition, tobi must be someone stronger than Madara. Izuna is weaker, so it can't be him. Tobi himself said he was the one who gave Nagato the rinnegan... and the only one we know of that had rinnegan then so6p (son had twister, not rinnegan).
Have many other reasons that actually makes it likely that Tobi is so6p, so if you want me to explain it, I do it often,
Not good english, sorry. I'm from Norway so you can't expect much
