Board Thread:Naruto Discussions/@comment-11276487-20140818181748/@comment-1087196-20141020030931

There is nothing even remotely hinting that Hamura became evil and Hagoromo never mentioned his brother in negative light, he would also lack the impact of a canonical villain if he simply poped out of nowhere with a random plot to crash the Moon.

It's either Sasuke, Kaguya or her successor who is causing this and it will probably tie in with the canon mythos about how Shinobi came into being.