I noticed he falls into this pattern of almost always lending money to people who he is fully aware will never be able to pay him back. I think sending Arthur to break their legs is more about preserving his ruthless reputation rather than actually expecting to make a profit, which if he was more successful in his endeavors would be understandable, but instead he just hemorrhages the gangs money on dead ends that barely break even at best, enjoys preying on desperate people, and excuses himself by blaming the debtors for even dealing with him in the first place. All that being said, I say Strauss is indecisive, cruel, cowardly and not nearly as smart as he thinks he is.
