While it is celebratory, it is not a casual result of chance. Much preparation occurred before hand, including the ministry of Jesus, when the Disciples arrived, and much earlier, with sharing prophecies in the temples.
And many spread their coats in the road, and others spread leafy branches which they had cut from the fields. Those who went in front and those who followed were shouting: “Hosanna Blessed is He who comes in the name of the Lord; Blessed is the coming kingdom of our father David; Hosanna in the highest!”
Mark 11: 8-10