What led to the German defeat of World War 1?

The magnificent efforts of the allies on both the western and eastern fronts was the reason for the victory of defeating the enemy.

Germany is in an unfortunate position. They have constantly been forced to fight wars on two fronts, against UK/French armies on their West, and Russians to the East. This divides their troops.

Germany got a massive boon in 1917 when Russia sued for peace, and Germany could move all their troops against France - but by that time America's sheer weight of numbers was entering the war, overwhelming the German armies.