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THIS IS JUST THE OVERALL
CONCLUSION THAT I CAME TO THE REASON BEHIND THEM ARE IN THE LINK PROVIDED ABOVE.
Madara gained hashis dna durring their battle a fact pointed out in the manga
and developed the rinnegan shortly before his death.some will say that does not explain why he lived so long and on the contrary it does.The members of this clan possessed both incredible longevity and life force.Their longevity can be seen in part through Mito, who lived from long before the founding of Konoha, to well into the term of the Third Hokage's reign. through her longevity and strong life force madaras life was extended due *inheriting the Sage's "body" — life force and physical energy.Having both strands of dna his blood was restored to its original roots and was granted the same longevity and life force and as a result extened his life.Acquiring the senju DNA essentially brought the blood to its purest form which was the uzamaki bloodline.Which led madara to eventually awaken the rinnegan.
As noted beore the uzamaki were also masters of fuininjustu.Now for someone who wants the fox a clan with the abilty to seal the tailed beast were a big threat to tobi/maradaras plan.They were alive before the first world war seeing how hashi has his pic taken with the clan leader.then they magically all die between the first war and third war seems like a coincidence ? I hardly think so.madara then sought out the refugee nagato and placed his eyes in him as storage.Now this theory makes logical sense and its also backed up by the fact that madara states in the manga that he was expecting to be brought back by nagato.Now if he did not live long enough then how did he know of nagato if he died before he was born ?The obvious answer is he did not die.Madara then placed the eyes in Nagato the refugee who was the only person left with the right dna to utilize the eye since he was an UZAMAKI AND HAD THE PURE unadulterated BLOODLINE OF THE SAGE WITHIN HIM.
We know tobi has claimed to be madara and a shell of his former seal.What i am proposing is madara used the rinnegan to create zetsu.The process he used is explained to have initially involved the administration of imagination, and the spiritual energy which forms the basis of Yin chakra to create shape and form from nothingness. Then, through the application of vitality, and the physical energy which forms the basis of Yang chakra, he would breathe life into the prior form.(which is why zetsu is back and white his color scheme is a symbolic representation of yin and yang) THE ZETSU PARTS WERE MERGED WITH OBITOS BODY TO HAVE IT SUSTAINED.I beleive that the body is indeed obito's but the path of madra a bit of his soul resides in him making the shell of his former self explination that much more reasonable.Now where orochimaru fits into this part i have not exactly found out but knowing that orochimaru knew pretty much everything about the rinnegan and the fact he already knows how to extract parts of his soul makes him a pretty good partner for tobi or should i say madara to have.Orochimaru already said he worked with tobi he used his knowledge to help madara contain his soul in obito.why ? Well what do you think orochimaru wants ?The sharingan at first i thought but no his goal was ultimately the rinnegan which is known to make learning justu a peice of cake and what did orochimaru originally want ? to learn all justu and the only way for him to do that was to expand his life.Now what eye do you know makes justu easy to learn and could possibly extend your life ?THE RINNEGAN.