Near the end of Ben Hur, as Judah Ben-Hur and Balthasar stand broken and weary at the feet of the crucified Jesus, Balthasar explains how in this act of self-sacrifice Jesus took upon himself the sins of all mankind. This may have been powerful moviemaking but it was terrible history. Okay, he was a wise man, but how exactly he worked out over two centuries of Christian theology in just two minutes was never adequately explained. But given the context of the times, maybe William Wyler didn't have to do much explaining; that Jesus died for our sins was a social given in 1959. One of the strengths of recent historical Jesus scholarship is its insistence on understanding the "Jesus event" in its own social/political/religious context -- a context that knew nothing of Christian theology.
A moment's reflection will tell you that the standard Sunday school answer to the question "Why was Jesus crucified?" (for man's salvation, eternal life, to reconcile humanity to God, etc.) would have made little sense to those directly involved in the event itself. Imagine you could travel back in time and cover the crucifixion as a reporter today might cover the protests in the Middle East. If you asked Pontius Pilate, Caiaphas or members of the crowd the reason behind this condemnation could any of them have muttered anything remotely like what most Christians say today? Very unlikely for the simple reason that this answer is born out of Christian theology -- something that did not exist at the time of Jesus.
So if we are going to get at why Pilate ordered Jesus to be crucified, Christian theology does us no good. Instead we have to look at why the Romans crucified people (in general) and why Pilate must have believed that Jesus (in particular) deserved this punishment. First, let's be clear. The fact that Jesus was crucified tells us that Rome was ultimately responsible for his execution. The Romans reserved this singularly brutal form of death for their exclusive use. If the Jews were going to execute someone they might behead (think John the Baptist) or stone them (think Stephen), but they didn't crucify them (for two interesting exceptions, however, see J.D. Crossan's book The Birth of Christianity, pp. 541-543).
Under Roman law, three offenders were most likely to be crucified: pirates, rebellious slaves and enemies of the state. Note well what all these have in common: a direct challenge to Roman authority. Crucifixion was public torture designed to pound home an unambiguous message: Don't mess with Rome. Obviously, Jesus was neither a pirate nor a rebellious slave. So now our historical question becomes more specific: Why did Pilate come to believe that Jesus was an enemy of the Roman Empire? How could one little peasant preaching love of one's enemies be seen as a threat to an empire whose armored legions spanned three continents? (Note: one should also be skeptical of Pilate as a wet-noodle weakling pushed about by cunning Jewish leaders and rowdy crowds. History suggests otherwise, although later gospel writers may have had good reasons to play him up somewhat differently than what he probably was.)
The problem with Jesus (from Rome's perspective) was that he didn't just preach loving kindness. He also preached justice -- and it wasn't Rome's justice; it was God's justice. Following in the footsteps of Albert Schweitzer, historical Jesus scholar Bart Ehrman argues that Jesus was understood by his contemporaries as a Jewish apocalyptic prophet. The kingdom of God was at hand, he proclaimed. This meant that God was soon to intervene in human affairs in order to correct a world that had gone badly awry. The first shall be last and the humble shall be exalted when this divine kingdom is fully realized. Needless to say the Romans were not too keen on hearing that their day had faded and they ought to consider a more humble approach to foreign policy. They were perfectly content with their form of justice. God's justice was not on their agenda.
Another influential scholar, John Dominic Crossan, sees Jesus as more of a Jewish cynic sage rather than an apocalypticist. The Cynics were philosophers who argued that true happiness could be found only by rejecting social conventions and living simple, uncluttered lives. Roman commercialism had corrupted Jewish society, Jesus argued. A few were getting very rich cooperating with the Romans while most were being dispossessed and taxed to death. This rupture in the Jewish community was threatening their relationship with God. The Jewish people were supposed to be a people of righteousness and justice, worshipping a God of righteousness and justice. But under Roman rule, their society was becoming just like all the others -- a wealthy arrogant elite grinding down on an increasingly desperate working class. As prophets throughout the ages had done, God was calling the Jews back to himself once again through Jesus. Only this time, there was nasty catch -- they had to stop cooperating with Rome. You can't serve both God and mammon.
Whether in his time Jesus was better understood as an apocalyptic prophet or a cynic sage, either one of them would have made him subversive. When he dispatched the money changers from the Jerusalem temple, he went too far. He did exactly what candidates for crucifixion do: he directly challenged Rome's authority (that authority being exercised through the Temple priests). As Crossan concludes in his book The Birth of Christianity , Pilate got it right. Jesus was subversive; more so than he could ever have imagined. Preaching compassion often gets you canonized. Preaching justice often gets you crucified.