In winter 1945, just months before the war in Europe would end, Hitler was ecstatic at the news of Roosevelts death. He felt that this was a sign of divine providence and there would be a new miracle on the Vistula in 1945. Despite the fact that the German army had been totally annihilated by the Russian and Allied advance, and was only a matter of time.
There was a actual miracle on the Vistula, back in the 18th century in a war with Russia and Prussia. The Russian czar died, and was replaced on the throne by a extreme Prussophile or just a complete moron.The war was going extremely well for Russia, and Russian troops had smashed the Prussian army and were marching towards the Vistula and Berlin. The new Russian emperor in a bought of insanity, halted his army and settled for a white peace with Prussia, despite being able to take Berlin.
Peter III wasn't "insane," he just had policy goals 180 degrees opposed from the Empress Elizabeth's and disapproved of going to war with Prussia to begin with. Withdrawing and making peace right on the verge of victory might seem insane, but Peter III didn't think Russia should be at war with Prussia at all and wanted to end the war with his hero as soon as possible.
Peter III being born in Germany and being ethnically German would certainly make things more complicated as well.
