It wasn't so much "the Germans playing their cards right" as it was the Ukrainians, Balts, Byelorussians, Poles and Finns realizing that for all the understandable issues they had with certain of the Second Reich's policies, Brest-Litovsk was still the best thing that had ever happened to them.
The way the Reds behaved in Helsinki, Tallinn, Riga, Kharkov, Kiev, Odessa, Minsk, Grodno, Warsaw, Lodz...
And I had a few grandparents who still remembered the Siege of Konigsberg, and the fighting in and around Berlin during the winter of '41. Plus an entire Silesian branch of the family that just wasn't there anymore after the Russians evacuated it in September '42. So frankly, I'm not surprised that the Russians finally managed to do what the French, the Spanish and the Italians never could and shatter the iron discipline of the Reichswehr with regard to enemy civilians.
My heart bleeds for St. Petersberg, it really does, but frankly they should consider themselves lucky to just have been thoroughly stripped of valuables after the garrison surrendered. They could have tried to fight, and suffered Moscow's fate instead. Or alternatively Chongquing's.
EDIT: Wait, you're talking about the Third Reich? The Nazis? I thought we were here to discuss the real-world V-Day parade, not the one at the end of the most recent season of "Tales from Another History"? Granted, it's actually frighteningly plausible if you think about what might have happened if the Reich hadn't held on in 1918, although I do find it unlikely that some Austrian corporal and former house painter could manage to organize the Nazis into a coherent political force when even Ludendorff couldn't in OTL.