A few years ago the media went wild over the ‘Gospel of Judas,” a gnostic text which (it was claimed) described Judas as a faith disciple of Jesus, chosen to be the betrayer because he was so faithful. I first encountered this idea through William Klassen’s book Judas: Betrayer or Friend of Jesus? (Minneapolis: Fortress, 1996). Klassen argued that Judas was not the betrayer, but rather the most faithful disciple. Jesus had to be handed over to the authorities, so he entrusted this job to Judas. In order to make this theory work, Klassen has to make the “anti-Judas” statements into “later additions” by the church. This includes the brief note in Luke that “Satan entered him” and the much later references to Judas as a thief in John’s gospel. He makes much of the fact that Paul never mentions the betrayal or Judas.
Another answer is that the “perfume incident” forced Judas to understand that Jesus was not the Messiah, at least exactly as he understood the Messiah. One option is that Judas was convinced by the anointing that Jesus was not who he claimed, and the Pharisees were right all along. Jesus had to be destroyed as a false teacher. A second option is that Judas was shocked when he finally understood that Jesus was literally going to his death. He may have expected Jesus to go to Jerusalem to overthrow the Romans, but not to die. He may have wanted to ‘force’ Jesus to use his power to destroy the Romans.
At the time of the Last Supper, Judas had already made his choice to betray when Satan entered him (Luke 22:3). Perhaps Satan’s hand in the betrayal was to tempt Judas into making the decision or perhaps to keep Judas from losing his nerve by entering him. This is an extremely unique event: Satan is never mentioned as “entering” anyone else. Satan has become personally involved because the previous efforts to stop Jesus have failed.
Another angle here is this: What did Satan stand to gain by getting Judas to betray Jesus? Why did Satan want to kill Jesus? He should have been able to understand that it would be Jesus’ death and resurrection that defeated him. Clearly Satan tried to stop him from going to the cross in the temptations, and tried to slow him down or stop him throughout his ministry, so why help him to the cross now? Satan’s role in the killing of Jesus is an indication of the arrogance of the devil. Perhaps he thought that if he could not stop Jesus in the world, that he could stop him in death. Maybe he thought that he could hold Jesus in the grave. Another option, although less likely, is that Satan was playing the role laid out for him, and that he was not truly a free agent in the whole affair.
Thirty pieces of silver was not a great deal of money, he would not have won many friends by betraying his teacher. I suspect that his motivations were good, he wanted to help Jesus establish himself as the Messiah and to assist him in starting a Kingdom of God in Jerusalem.
But from a purely human perspective, what did Judas hope to gain?
Bibliography: Klassen also wrote the Anchor Bible Dictionary article, “Judas Iscariot”, 3:1091-1096. For a more balanced approach, see D. J. Williams, “Judas Iscariot”, in DJG, 406-408; John P. Meier, A Marginal Jew, 3:208-211.