1. Palm Sunday is about peace and salvation
Each year during Passover, the then-Roman Governor Pontius Pilate would enter Jerusalem with his soldiers to show his strength through the arms his men carried. The presence of Pilate and the Roman soldiers was to thwart protests against Roman rule. Jesus, however, came on a donkey with all His disciples unarmed, to demonstrate the Kingdom of God and His peace.
It was customary that during a time of peace a king would ride on a donkey, while a king would come sitting on a white horse after the victory in a battle, as suggested in Judges 5:10 and 1 Kings 1:33. So Jesus came as King but not to judge the people. He came to demonstrate God's grace.