What does Matthew 27:30 mean?

The abuse of Jesus by a battalion of Roman soldiers was not complete even after they had sarcastically hailed Him as King of the Jews (Matthew 27:27–29). After torturing Jesus (John 19:1), they laughed at Him. They piled on more and more mockery. And then they gave Jesus one last beating, hitting the Lord with the reed they'd made Him hold as a mock scepter and spitting on Him. All of this corresponds to Jesus' predictions (Mark 10:34; Luke 18:32).

John's account places this moment ahead of Pilate's final decision to have Jesus crucified. Matthew is, again, grouping his gospel by theme rather than by time. Pilate brings Jesus out before the crowds dressed as a mock-king and presents Him to the people with the words, "Behold the man!" (John 19:4–5). It's likely Pilate hoped that when the people saw a ragged, mutilated, shamed figure, they would decide further cruelty was unneeded. Instead, it only seemed to increase their blood lust (John 19:6).