Eventually, Jesus came to Jerusalem. When people found out about it, a lot of people took out palm trees and cried out blessings for the one who came in the name of the Lord who is also the King of Israel. They proclaimed blessings out of belief, presumably from what Jesus did.
As Jesus came in, he was riding on a young donkey. Jesus did so likely because he knew God himself noted the plan of the King riding on the donkey (from Zechariah 9), and Jesus obeyed. The disciples at first did not know about the donkey thing at first, but eventually, after the glorification, they realized that Jesus was the fulfillment of many prophecies that promised someone now known as Jesus. God promised the King on the donkey, and Jesus fulfilled that promise.