What was the reason for Jesus’ Passion?

The Catechism of the Catholic Church (paragraphs 613-614) says,

Christ's death is both the Paschal sacrifice that accomplishes the definitive redemption of men, through “the Lamb of God, who takes away the sin of the world,” and the sacrifice of the New Covenant, which restores man to communion with God by reconciling him to God through the “blood of the covenant, which was poured out for many for the forgiveness of sins.”
This sacrifice of Christ is unique; it completes and surpasses all other sacrifices. First, it is a gift from God the Father himself, for the Father handed his Son over to sinners in order to reconcile us with himself. At the same time it is the offering of the Son of God made man, who in freedom and love offered his life to his Father through the Holy Spirit in reparation for our disobedience.