Old Enemies

Hikigaya understood this. 

The world power understood this and the world understood this. Win or lose, the world power will not crumble in one day

Hence the way of winning for the dark forces of the world is numerous. But the way for the world power to win is only one way

And that is the way that Death Monarch had decided. The objective of this war has always been determined by Death Monarch

He provokes this war because he believes he could win. It is different from the world powers conflict and this conflict

The world powers struggle against each other is different. 

To the people of the world, there might be a ranking of power between the world powers but there was never a person other than Death Monarch that could break the regulations set by the world powers.

A single person managed to suppress the world power is not exactly a common thing. And even then, Death Monarch is a part of the world powers