https://upload.wikimedia.org/wikipedia/commons/transcoded/b/b1/Selektion_in_Auschwitz.webm/Selektion_in_Auschwitz.webm.480p.vp9.webm
"The situation at the ramp did not allow any resistance from the victims; they were appeased or intimidated and left in the hope that it was a labor assignment or relocation. Firearms were "almost never" used there."
A few Guards for thousands of People.
Selection then "Delousing"-Entlausung- and there i think is the missing Part.
-Chemicals-Medicals-Drugs- to give up any resistance and go to the "Showers" and see the dark smoke from the Oven.
Just a thought.