New Defender's Study Bible Notes
21:9 the multitudes. These multitudes were unwittingly fulfilling Psalm 118:25-26 (“Hosanna” means “save now”). However, they only perceived Jesus as “the prophet of Nazareth of Galilee” (Matthew 21:11), and were evidently expecting Him somehow to defeat the Romans and restore the kingdom to Israel. People had frequently called Him “son of David,” evidently knowing about the genealogy of His (foster) father, and realizing He was the legal heir to David’s throne (see note on Matthew 1:16).
However, just five days later, these same multitudes—apparently disappointed by His meek submission to arrest and torture by the Jewish and Roman rulers—were calling for His crucifixion, preferring to release Barabbas who had led a rebellion against the Romans (Matthew 27:21-22).