Chapter 2: The Fallout of Restraint
The Fourth Shinobi World War was said to be the least destructive war of all time. This is counterintuitive, because how could the least destructive war eradicate all Shinobi? The reason for this is that the Village Hidden in the Leaves was the most peaceful Great Village.
This again is counterintuitive. The Village Hidden in the Leaves, being most peaceful, demanded less of its Shinobi. This made them less desiring to desert the Village, as was common with the other Great Villages. This also gave them ability to be moral, as the harsh climate of the other Villages denied any chance for morality. This meant that most, if not all, Shinobi from that Village had techniques which they did not use, as they were regards as unethical or morally wrong. These techniques usually required sacrifice, or caused immense loss of life. So, in simpler words, the Shinobi from the Village Hidden in the Leaves restrained themselves from their most dangerous techniques.
The person who held the Tailed Beast inside themselves was beloved by everyone in the Village Hidden in the Leaves, for obvious reasons. In addition, several prominent leople had close personal ties to this person. As a result, when he died, most, if not all, of the people that made up the Village Hidden in the Leaves were immensely saddened by his death.
...
"What was his name, Sensei?"
"We don't know the name of the person. Actually, we don't even know if they were male or female."
...
As an old philosopher has said, 'Sadness breeds anger, anger fury, and fury revenge.'
And that was what happened, and the Shinobi let go of their ethics, morality, and restraint. In a historian's more colloquial terms, 'They let it loose.'