Jesus Christ Superstar

The film is framed as a group of performers who travel to the desert to re-enact the Passion of Christ. The film begins with them arriving on a bus, assembling their props and getting into costume. One of the group is surrounded by the others, puts on a white robe and emerges as Jesus ("Overture").
Judas (Anderson) is worried about Jesus' popularity; he is being hailed as the Son of God, but Judas feels he is just a man who is beginning to believe his own propaganda and fears the consequences of their growing movement ("Heaven on Their Minds"). The other disciples badger Jesus for information about his plans for the future, but Jesus will not give them any ("What's the Buzz?"). Judas' arrival and subsequent declaration that Jesus should not associate with Mary dampens the mood ("Strange Thing Mystifying"). Angrily, Jesus tells Judas that he should leave Mary alone, because his slate is not clean. He then accuses all the apostles of not caring about him. That night at the Temple, Caiaphas is worried that the people will crown Jesus as king, which the Romans will take for an uprising. Annas tries to allay his fears, but he finally sees Caiaphas' point and suggests that he convene the council and explain his fears to them; Caiaphas agrees ("Then We Are Decided"). As Jesus and his apostles settle for the night, Mary soothes him with some expensive ointment, but Judas says that the money spent should have been given to the poor. Jesus rebukes him again, telling him that the poor will be there always but Jesus will not ("Everything's Alright").
The next day at the Temple of Jerusalem, the council of the priests discuss their fears about Jesus. Caiaphas tells them that there is only one solution: like John the Baptist, Jesus must be executed for the sake of the nation ("This Jesus Must Die"). Jesus and his followers joyfully arrive in Jerusalem, but Caiaphas orders Jesus to disband the crowd for fear of a riot. Jesus refuses and speaks to the crowd ("Hosanna"). Later, the apostle Simon Zealotes (Marshall) and a crowd of followers voice their admiration for Jesus ("Simon Zealotes"). Jesus appreciates this, but becomes worried when Simon suggests directing the crowd towards an uprising against their Roman occupiers. Jesus sadly dismisses this suggestion, saying that they do not understand His true purpose ("Poor Jerusalem").
Pilate, the Roman governor of Judea, reveals that he has dreamed about a Galilean man (Jesus) and that he will be blamed for this man's death ("Pilate's Dream"). Jesus and his followers arrive at the temple, which has been taken over by money changers and prostitutes ("The Temple"). To Judas' horror and as the priests watch in the background, a furious Jesus destroys the stalls and forces them to leave. Jesus wanders alone outside the city, but is surrounded by a crowd of lepers, all wanting to be healed. Jesus tries to heal as many of them as possible, but is overwhelmed by the sheer numbers and eventually gives up, screaming at them to leave him alone. Mary comforts Jesus and Jesus goes to sleep. Mary loves Jesus, but is confused because he is so unlike any other man she has met ("I Don't Know How to Love Him"). Judas goes to the priests and expresses his concerns, but he is worried about the consequences of betraying Jesus ("Damned for All Time"). The priests take advantage of his doubts and offer him money if he will lead them to Jesus. Judas initially refuses, but Caiaphas and Annas win him over by reminding him that he could use the money to help the poor. Judas reveals that Jesus will be at the Garden of Gethsemene on Thursday night ("Blood Money").
At the Last Supper (set outdoors in a garden setting during the day), Jesus reveals that he knows Peter (Toubus) will deny him and Judas will betray him. A bitter argument between Jesus and Judas ensues, in which Judas berates Jesus for destroying their hopes and ideals and threatens to ruin Jesus' ambition by staying there without helping him to reach the Glory; Jesus tells Judas to leave and Judas finally runs off ("The Last Supper"). As the apostles fall asleep, Jesus goes to Gethsemane to pray about his imminent death and reluctantly agrees to go forward with God's plan ("Gethsemane [I Only Want to Say]"). Jesus waits for Judas, who arrives, accompanied by guards, and betrays him with a kiss. The disciples offer to fight the guards, but Jesus will not allow it. Jesus is taken to Caiaphas' house, found guilty of blasphemy and sent to Pilate ("The Arrest"). Peter, meanwhile, fearfully denies Jesus three times after being accused of being one of Jesus' followers ("Peter's Denial"). Jesus is taken to Pilate's house, where the governor, unaware that Jesus is the man from his dream, mocks him. Since he does not deal with Jews, Pilate sends him to Herod ("Pilate and Christ"). The flamboyant King Herod is excited to finally meet Jesus, for he has heard the hype. He tries to persuade Jesus to perform various miracles. When Jesus refuses to answer, Herod orders the guards to take him back to Pilate ("Herod's Song [Try It and See]").
The apostles and Mary Magdalene remember how things began and wish that they had not gotten so out of hand ("Could We Start Again Please?"). Jesus is flung into a cell, where he is seen by Judas, who runs to tell the priests that he regrets his part in the arrest. He hurls his money to the ground and curses at the priests before running into the desert. Filled with regret for betraying Jesus, he blames God for his woes by giving him the role of the betrayor and hangs himself ("Judas' Death"). Jesus is taken back to Pilate, who questions him; Herod is also present. Although he thinks Jesus is deluded, Pilate realizes that he has committed no actual crime and has Jesus scourged; Herod is gleeful at first but eventually sickened. Pilate's bemused indifference turns to a frenzy of confusion and anger, both at the crowd's irrational bloodthirstiness and Jesus' inexplicable resignation and refusal to defend himself. Pilate realizes he has no option but to have Jesus executed or the masses will grow violent ("Trial Before Pilate [Including the Thirty-Nine Lashes]"). After Pilate washes his hands of Jesus' fate, Jesus' appearance transforms, the heavens open, and a white-jumpsuit clad Judas descends on a silver cross. Judas laments that if Jesus had returned as the Messiah today, he would have been more popular and his message easier to spread. Judas also wonders what Jesus thinks of other religions' prophets. He ultimately wants to know if Jesus thinks he is who they say he is ("Superstar"). Judas' questions go unanswered, and Jesus is sent to die ("The Crucifixion"), with ominous, atonal music, with Jesus saying some of his final words before dying.
As the film ends, the performers, now out of costume, board their bus (the performers who played Mary Magdalene and Judas last of all), with "Pilate", "Mary Magdalene" and "Judas" the only ones looking back towards something off-screen as they board, and drive away, but Jesus is notably absent (Neeley had already stripped away his costume and disappeared into the cast beforehand). The final shot of the film shows the empty cross against a setting sun, as a shepherd and his flock cross the hillside ("John Nineteen Forty-One").

Question: Why does Caiaphas say Jesus must be executed?
Answer: Sake of the nation