Now it was the day of Preparation of the Passover. It was about the sixth hour. He said to the Jews, “Behold your King!” They cried out, “Away with him, away with him, crucify him!” Pilate said to them, “Shall I crucify your King?” The chief priests answered, “We have no king but Caesar.”
(John 19:14-15 ESV)
Pilate’s motivation is not clear, but it seems as though he is trying to spare Jesus’ life by making him seem as little like a king as possible - slapping, mocking, flogging, crown of thorns, purple robe - when he says 'behold your king' they are looking at a pathetic specimen.
Their response, that they have “no king but Caesar” - shows they are willing to say anything to have Jesus killed. They hate the Roman Empire, these words must have stuck in their throat, but for them it’s not enough to humiliate him, they want him out of the picture entirely. This is not a technical matter of the law, they don’t want a king that challenges their position. As they said in 12:19 the whole world is going after him, and they needed to stop that.
We are the same. We don’t want a king. We want to be our own king. Jesus is the ultimate King, regardless of what we want, but he is also willing to go to the cross for us.
“the essence of sin is man substituting himself for God, while the essence of salvation is God substituting himself for man. Man asserts himself against God and puts himself where only God deserves to be; God sacrifices himself for man and puts himself where only man deserves to be. Man claims prerogatives which belong to God alone; God accepts penalties which belong to man alone.” John Stott