According to my understanding of Satan’s perception of victory at the Cross, was it because he, like the Temple hierarchy, expected only a conquering King when Messiah came? That is, Satan did not understand the dual nature of Jesus’ coming to earth, first as the Suffering Servant, and only then, much later, as the King. Therefore, when he killed Jesus on the Cross, he believed he had thwarted God’s plan for the Messiah to become King of the earth, and it would be back to the drawing board for God. Have I got it right?
The big surprise that turned what Satan thought was his greatest victory into a resounding defeat was God’s agreement to accept the death of His Son as payment in full for all the sins of the entire human race. He thought he had God boxed in.
Some speculate Satan had said in effect, “You can’t be righteous and holy and still accept them, and you can’t be merciful and loving and still judge them.” But when he saw our sins nailed to the cross he knew he’d been had. Now God’s righteousness and His love were no longer in conflict. He could accept us and didn’t have to judge us. Paul said that this made a public spectacle of Satan (Col. 2:15) and if he’d known about it in advance he would never have let the Lord be crucified. (1 Cor. 2:8)