The Germans were not in the habit of giving up cities without a fight
Krakow was an exception. Germans didn`t intend to defend it or blow up in revenge.
That was the effect of the magic stone which is hidden in the Wawel Hill. Thanks to its magical aura, Krakow is fully protected and will never be destroyed.
That is why when Russians attack Poland, I will get my family back to Krakow and myself go to the war.