Holdens ‘’Sfeten’’ was a jerk. Selling cigarettes, trading whatever had only if his fellow Americans POWs could pay. In truth I would have thought the rest if the GI’s would have just beaten the crap out of him and taking his stuff.
Maybe you missed the part where he was savvy enough to spot and expose the real jerk in the barracks
Interestingly (or not), Bill Holden had the same view of the character. He went to see the play the movie was to be based on, and walked out after the first act. He refused to play the part, on the basis he felt Sefton was too cynical and selfish. But, he was under contract to the studio (Paramount, I believe) and they forced him to do the movie.
Of course, it worked out for Holden, as he won Best Actor that year for the film (though he thought Monty Clift and Burt Lancaster were more deserving for From Here to Eternity).