They assume that it is a case of God exacting retributive justice on Job for something Job had done. Ahab wishes to exact this type of justice on the white whale, but this quest for justice becomes a quest for vengeance. Job had no worldly objects at which he could direct his anger, but there was something on which Ahab could focus his vengeance and he took the opportunity to do so. For Ahab, the whale becomes the symbol, the worldly incarnation of the God or fate that had stripped him of his leg. Thus, the whale hunt is for Ahab mostly about vengeance.
Job avoids vengeance.
Job will not curse God, he will not lash out with any anger he may have. He questions God, but never turns against him. Though Melville puts Ahab through tests similar to Job's, Ahab has a very different personality than Job. Ahab desires vengeance. Moby Dick had reaped away Ahab's leg. . . .