The manga is becoming more and more strange, the first hokage inside the wood monster? Didn't they say he died in a battle field? What is that? We will all going to find out.
My theary is that Marada is not Obito nor Marada infact I think he is a copy that went bad. I think someone taken DNA semples from diffrent Ninjas and made him to be the "high Ninja". However he was used and had been abended, than he started to think how to distroy all things that he had been creat to protect.
But that is what I think, what do you think?