It was blown up by the Soviets, as it had been very badly damaged by the Germans during the war. Why they demolished it I cannot imagine. The other Palaces were also very badly damaged and they managed to rebuild those. Unless of course if it was just a pile of rubble.
I think this palace is every bit as important architecturally as the Alexander Palace, and another beautiful example of why Quarenghi was so highly regarded as an architect, both during his lifetime, and today.
It really is very sad that this building has been lost. It was magnificent.