Genocide

How come no one ever steps in and help during a genocide. The Armenian genocide, Rwandan, Ukrainian "genocide", and there was some help in the holocaust. in the Rwandan genocide, when the hutus were being slaughtered, the U.N. came but just stood there and did not fire one bullet. And the countries who perform the genocide arent severely punished or not punished at all like the Turks after the armenian genocide.