How did the roman culture make it possible for caesar to become a human god?

The positioning of Caesar as a god in Roman culture was made possible by the act of Octavian, who was Caesar's adopted son and heir to his throne. Octavian encouraged Romans to view Caesar as a god by building shrines, temples, and statues to Caesar, just as they would a god.  Octavian did so in order to legitimize his own position as ruler and to suggest that he was supported by Caesar, in essence, from beyond the grade (given that he was now a god).  

Because broadest terms allows the law flexibility depending on changing society and circumstances.