What does Luke 23:21 mean?

This is music to the ears of the chief priests, elders, and scribes. Hours before, they had followed Judas to the Mount of Olives to arrest Jesus. They went in the dark of night, knowing that if they tried to arrest Him in broad daylight, the people would rebel against them (Luke 22:1–2).

They need it to seem as if the people are on their side. They don't need all the people. Just as in modern politics, the loudest, angriest, and most immediate voices are the first to be heard. The mob's presence is enough for Pilate to worry about a riot. Pilate understands that the leaders are persecuting Jesus because they're jealous of His popularity (Matthew 27:18; Mark 15:10). Pilate has the authority to decide who will hold the position of high priest. Caiaphas held that rank for nearly twenty years, suggesting he and Pilate get along very well. But if Jesus draws the people away from the priests, the priests will lose influence and Pilate may take away their authority (John 11:48). They could lose everything.

So, the religious leaders perform a brazen feat of hypocrisy. They charge Jesus with attempted insurrection (Luke 23:1–5) while they agitate a throng threatening to start an insurrection (Matthew 27:24), unless Pilate releases a man convicted of insurrection (Luke 23:19). If the Jewish leaders can get a Roman governor to remove Jesus using a Roman execution, they can minimize the evidence of their involvement.

Pilate isn't done, however. The injustice against Jesus is so overblown that he tries one more time. The crowd will hear none of it. The crowd shouts Pilate down until he agrees to crucify Jesus (Luke 23:22–25).