Here is additional clarification of the Buchenwald status of Eugen Kogon so ably begun by Walter Felscher. Kogon was an Austrian economist and journalist who wrote a dissertation under Othmar Spann. He was arrested in March, 1938, and kept in a number of prisons before he was transferred to Buchenwald in September 1939. His status there was as one of the KOMMANDIERTE (not KAPOS) -- as a clerk in prison hospital. "He served as a private secretary to Dr. Erwin Ding-Schuler, the camp doctor, starting in April 1943. In this post he acquired detailed knowledge of the medical experiments conducted on prisoners. As one of the more knowledgeable prisoners, he was placed on the list of forty-six 'anti-fascists' to be executed in April 1945 before evacuation of the camp." (Hackett, David A. THE BUCHENWALD REPORT. Boulder: Westview, 1995, p. 16). The word KAPO is derived from the Italian capo (as, I think most of us know from the American gangster literature), and it is defined as the "prisoner leader of a work detail or other administrative unit." (p. 379).
The central question of the motivation of various sadists in and out of Buchenwald can probably be answered only, if at all, by examining the defendents' statements in various trials. This investigation should have been completed by various responsible Germans, preferably with legal training, long ago.
Here is an account which bears on that central issue. It was written by General Chuck Yeager. Yeager (the name was at one time spelled Jaeger) is not only a very famous test pilot but a former Mustang P-51 fighter pilot in World War II and a 100% American from the Great State of West Virginia. Here is Jaeger/Yeager on one experience of Yeager the Jaeger:
Atrocities were committed by both sides. That fall  our fighter group received orders from the Eighth Air Force to stage a maximum effort. Our seventy-five Mustangs were assigned an area of fifty miles by fifty miles inside Germany and ordered to strafe anything that moved. The object was to demoralize the German population. Nobody asked our opinion about whether we were actually demoralizing the survivors or maybe enraging them to stage their own maximum effort in behalf of the Nazi war effort. We weren't asked how we felt zapping people. It was a miserable, dirty mission, but we all took off on time and did it. If it occurred to anyone to refuse to participate (nobody refused, as I recall) that person would probably have been court-martialed. I remember sitting next to Bochkay at the briefing and whispering to him: "If we're gonna do things like this, we sure as hell better make sure we're on the winning side." That's still my view. (Yeager, Chuck. YEAGER, AN AUTOBIOGRAPHY. New York: Bantam Books, 1985, pp. 62-63)