There is one thing to add to the mix - and that is that Nazi genocidial fixations were a net military disadvantage to them, in all sorts of ways.
Comming at this from the POV of a cold hearted bastard intent on nothing more than defeating mine Nazi enemies, allowing the Nazis to go full steam ahead in their self-defeating plans makes some sort of sense. When the Russian front was screaming for rolling stock, using railroads to transport Jews, Roma and other undesireables around the countryside instead of ammunition to the front was sheer lunacy on the Nazi part … not to mention all of the industrial resources used to construct huge slave-run factories that never produced anything much of value (see for example the insider’s account by Primo Levi about the overall worthlessness of I.G. Farbin using death camp inmates).
Allowing the Nazis to waste their time and resources on this folly, while smashing the actual productive bits of the Nazi regime, makes a certain amount of sense. Though I agree that, if they chose, the Allies could have disrupted the Nazi death camp regime badly.