My theory is pretty simple; we all know that Madara did in fact say there would be darkness that would happen from the villages and this would also play a large roll from him knowing that even though clan and people have been brought together the villages are coping and still would play a roll in fighting and even though the clans would stop fighting the villages wouldn't (his prediction of darkenss; which I believe is what he ment) knowing how people an ninja are.
My theory is that Madara wanted to take Hashi's dream of peace and take it a step further and truly make world piece by bring together all the villages as one unit (Shinobi Alliance). For Madara to do this he had to create 1 common enemy so powerful that it would force the Villages to unite under the one common goal; defeat Madara. He knew he could play the villain since most of his clan members didn't want to follow him, Senju member didn't trust him, and the Uchiha name was known as well as Madara himself.
Obito's roll, Madara knew he couldn't live forever and needed someone he could influence and bring to light his dream of world piece; he took in Obito told him about his plan of the Infiniate Tsy, which would bring piece through out the land (hints the world piece), knowing his life was coming to an end and why he worked so hard to stay a live, implanting the Rinnegan into Nagato who lived in a village under constant war, and placing all his pieces in order to be reborn once Nagato brought him back to life, Edo wasn't even a part of the plan just ended up working in his favor.
Obito wanted to activate the Infinate Tsy, But they have not done so yet.
Think about Code Geass, he did the same thing to bring world piece by becoming the enemy of everyone.
My theory is that Madara wanted to take Hashi's dream of peace and take it a step further and truly make world piece by bring together all the villages as one unit (Shinobi Alliance). For Madara to do this he had to create 1 common enemy so powerful that it would force the Villages to unite under the one common goal; defeat Madara. He knew he could play the villain since most of his clan members didn't want to follow him, Senju member didn't trust him, and the Uchiha name was known as well as Madara himself.
Obito's roll, Madara knew he couldn't live forever and needed someone he could influence and bring to light his dream of world piece; he took in Obito told him about his plan of the Infiniate Tsy, which would bring piece through out the land (hints the world piece), knowing his life was coming to an end and why he worked so hard to stay a live, implanting the Rinnegan into Nagato who lived in a village under constant war, and placing all his pieces in order to be reborn once Nagato brought him back to life, Edo wasn't even a part of the plan just ended up working in his favor.
Obito wanted to activate the Infinate Tsy, But they have not done so yet.
Think about Code Geass, he did the same thing to bring world piece by becoming the enemy of everyone.