Events leading to the german surrender included all of the following except:
collapse of turkey and bulgaria
united states joining the allies
split of austria-hungary
allies forcing the german retreat
threat to the german homeland
surrender of russia

Surrender of Russia.

Russia did not surrender during the WWII, in fact, it was the Red Army the one that caught first Berlin.

The events which didn't lead to the surrender of Germany was infact the surrender of Russia. The reason why this is the correct answer is because they felt that with Russia surrendering, they were finally free on the Eastern front and could finally strike on the Western front as well.