Even Madara doesn't know how Obito survived. Trololololololol...
Setting up the return of Kakashi's eye to Obito as Obito turns good. Yeah!
Also, you guys are focusing on the wrong plot hole (or at least, a stupid plot). Madara awakened the rinnegan before his "death" and then loaned the eyes to who turned out to be Nagato... who awakened the eyes as a child when his parents were murdered. Which means... Madara slotted his eyes into a child with no knowledge of the kid's future motivation and/or skill.
Holy crap. Think I made a joke post about that. I should go find it.
A simple souvenir of someone's kill
And like the sea
I'm constantly changing from calm to ill
Madness fills my heart and soul as if the great divide could swallow me whole
oh, how I'm breaking down