You are correct, too, the most likely to carry out such orders were picked. But Germany didn’t have that many “thugs” These folks doing the study fail to point out the consequences of disobeying orders in those days.
I’m not so sure that consequences for disobedience were as much a factor as was cultural obedience.
Even today, in Germany, police officers to not talk or chat with you. Everything they say is an order that they expect to be obeyed. There is a great sense of orderliness.
And this can get rather bizarre. For example, while the German military was supposed to have iron discipline in following orders, soldiers down to privates were required to show initiative when initiative was important, and they would be punished if they failed to do so.
Paradoxical. Yet it meant that they were hesitant when encountering unknowns in the offense, since in that case obeying orders was paramount; but in the defense, initiative was king, so Germans were extremely hard to fight when they were in defense.
It has been noted that the Nazis were indeed brutal against individual defiance; yet they became almost paralyzed when confronted with group defiance.
For example, a prison was filled with political prisoners, and a mob of their wives and mothers formed outside of the prison. The Nazis were immobile in the face of this group of women, who eventually walked into the prison, let their husbands and sons out, and took them home, and the prison authorities just stood there.
There were other incidents similar to this.