Although the Sage of Six Paths' physical body had died, he had scattered Chakra throughout the entire ninja world, watching over it in a special way.
Therefore, there was nothing in this world he did not know, including all of Black Zetsu's little schemes.
The reason he did this was to carry out a great mission... His mother, Kaguya, was immortal. He had to prevent her from breaking free of the Seal, as well as any signs that might lead to it.
Chen had always found it strange. How could the Sage of Six Paths and his younger brother be so ruthless toward their own mother, Kaguya? So it was because they had the whole of humanity and the Earth in mind.
But that was indeed the truth. Back when Kaguya was still alive, she had already been raising humans like livestock and creating batch after batch of White Zetsu armies.
Those White Zetsu absorbed the Earth's energy day and night to power the Divine Tree.
As a native creature of the Earth, the Toad Sage could not tolerate that. If the Earth was finished, so was he.
That was no baseless worry.
Gamamaru was a long-lived creature, and his life had only just begun.
Other creatures lived at most a hundred years before kicking the bucket, so naturally they would not care about the Earth's ecological problems hundreds or even thousands of years in the future.
But Gamamaru was different. He could live for thousands, even tens of thousands, of years.
With Kaguya's unyielding nature, if she kept absorbing energy like that, the Earth might not even outlast Gamamaru.
So, he urged Kaguya's son Hagoromo to rebel against his mother.
Hagoromo agreed as well. If one had to ask why, it was probably because... he loved this land too