Why do you think Dubro is not a source of any credibility?

Police believe Renda may have been killed because of a debt he owed to someone. For all we know, the Bonanno family had sanctioned his murder. Desjardins was put in isolation for a while because his life was in danger. Di Maulo may have thought he had nothing to fear and did not need protection, but as you know that has cost him his life.