Russia's withdrawal from the war hurt the Allies because it weakened the Eastern Front, allowing Germany to focus its military efforts on the Western Front and potentially gain the upper hand in the conflict. This forced the Allies to divert more resources and troops to the Eastern Front to compensate for the loss of Russian troops, which strained their already limited resources. Additionally, Russia's withdrawal also meant that the Allies lost a key ally and source of military support, further weakening their overall position in the war.
