Palm Sunday marks the beginning of Holy Week. Holy Week is the last week of Lent, and thus is the week leading up to Easter. As such, it is a time to reflect upon the Death and Resurrection of Jesus with particular intensity.
In most Catholic Churches, at least of the Latin Rite, it is traditional to read stories from the Passion narrative. I think there is an important lesson to learn here. By reading the Passion narrative on Palm Sunday, we see the contrast between what transpired on these two days: those same people who welcomed Jesus in a kingly manner on Palm Sunday were the same people who chose Barabbas over Him just a few days later.
A lot of people reading the Gospels may say, “What hypocrites!” Others, seeing how Jesus’ death was initiated by a traitorous disciple and executed by the collusion of various religious and political leaders among the Israelites and Romans, may say, “Poor people! How easily manipulated by whatever happens to please them at that moment!”
The thing is, it is easy for people who have explicitly made the choice to accept Jesus, and who know Who Jesus Is, and who love Jesus, to say that. Such a person would, if present at the Way of the Cross, not be counted among those who would beat, spit on, or mock Jesus. In a word, hindsight is 20/20.