Hagoromo & his brother seales Kaguya's chakra inside the Tree/Shinju
The Shinju was first a tree, then after Kaguya stole it's chakra it became the Ten tails. We know that Hagoromo and his brother "fought" the beast and won. I have a feeling that Hagoromo and his brother turned on their power-mad mother and sealsed her chakra back into the Shinju, as compensation for her stealing it in the first place. They actually didn't defeat the Shinju, they only gave it back it's chakra. In return for this deed the Shinju would stop it's rampage and return to it's previous form as a tree. But this is when i think Hagoromo made the Shinju his jinchuuriki. His brother diagreed with Hagoromo and didn't want him to become a jinchuuriki, stating that no one should have that much power, refering to his mother and how it turned her in to a power-mad woman. Fearing the same would happen to Hagoromo, his brother tried to stop him, but failed. Thus Hagoromo had killed his own brother and become the most powerfull man alive.
This leaves us with a giant dilemma, was Hagoromo the "good brother" or in fact the greedy one? Was he wrong to tamper with the power of chakra and force his believes (ninshuu) on the people? Remember, without Hagoromo there would never had been chakra in this world in the first place. Maybe his brother wantet things to stay the way they where before Kaguya stole the chakra. As it tuned out, Hagoromo was in fact NOT the savior, his dream of ninshuu failed beacause it created wars over power/chakra.
Maybe his brother was right, and he was wrong in the end?