SO6P sealed Jubbi inside of him in order to protect the world from its terror and he was able to suppress its huge chakra and if was to die Jubbi would be free and once again terrorize the world so he used Yin-Yang ninjutsu to create 9 tailed beasts.......
During that it was not controlled so it just destroyed things at will but now it was controlled that doesn't justify its actions though....
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It would be epic if Naruto controls it but if its mindless and go on rampage then may naruto will become its Jinchurikki
I would also like to read your theory about jubbi..........