Albert Barnes Commentary Matthew 27:23

"And he said, Why, what evil hath he done? But they cried out exceedingly, saying, Let him be crucified." — Matthew 27:23 (ASV)

And the governor said, Why? Luke informs us that Pilate put this question to them three times, so anxious was he to release him. He affirmed that he had found no cause of death in him. Therefore, he said that he would chastise him and let him go.

He probably expected that by having him publicly whipped, he would arouse their compassion, satisfy them, and thus evade the demands of the priests and release him with the people's consent.

So weak and irresolute was this Roman governor! Satisfied of his innocence, he should have immediately preferred justice to popularity and acted as was fitting for a magistrate in acquitting the innocent.

Let him be crucified. See the commentary on Matthew 27:39.

Luke says they were insistent with loud voices demanding this. They urged it. They demanded it with a popular clamor.