Just finished reading the Monuments Men book last night, and there's several chapters about the Nero Decree and its enforcement. In more than one location, sane German officials stopped the SS men from doing it, the best example being the Altaussee mine where the bulk of the stolen artwork by Hitler had been kept--we're talking the best of the best art, sculptures, et cetera. I think the level of cognitive dissonance required to do that is too extreme--few fanatics were left. Kaltenbrunner, Himmler, Göring, all of them had given up, fled, tried to open their own peace negotiations with the Allied forces. In the case of Altaussee, the miners, the mine director, and the head art official all rebelled against the fanatical gauleiter, smuggling out the bombs he'd placed in there and blowing the mine entrance to prevent the art from destruction. Speer refused to destroy the infrastructure.
I think a good point to keep in mind here that while there were a fair amount of fanatics, most of those were dead by this point. The bulk of the remaining people were the regular people and the opportunists, those who became Nazis for their own selfish gain, not because they believed in Hitler's eugenicist bullshit. Those people won't destroy their potential future to satisfy his last suicidal wishes.
So have the whole thing start kicking off with the (In TTL)Destruction of Paris. At that time there were more fanatics.