The Victorious Savior

How is this a picture of Representation with David as a type of Christ? How does natural man look at this from the view of the art of warfare only? How do men have it backward that Goliath is the powerful one? Why are all Goliath's armaments man made? What did David mean that he did not prove Saul's armor therefore he couldn't use it? What did David's staff represent? Why 5 smooth stones? Was David as a type of Christ the underdog in this battle? Did Satan believe he finally had Christ when he saw Him in the flesh? Was the victory sure? What was required for the salvation of the chosen?