Jerusalem was the goal of Our Blessed Lord’s mission on earth. In Jerusalem was accomplished the great work of redemption. The Sacrifice of Calvary wrought salvation for all people. Theologians call this the objective redemption. This is the manifestation of the universal salvific will. God wills all people to be saved and gives the grace necessary for each individual to be saved.
Saint Augustine notes that God who saved me with me will not save me without out me. God first acts upon a person to give the invitation to Eternal Life, then the person must respond. Human cooperation with Divine Providence is necessary for application of the objective (or universal) redemption to the individual. The theologians call this the subjective redemption because each individual must accept the invitation for him or herself. Contrary to what one might think, the accepting of the invitation is more than just receiving the grace of Divine Friendship in Baptism or being restored to it in the Sacrament of Penance. The process here involves the time of preparation where the soul, as it were, is courted by the Beloved. This is when a person receives the prevenient graces which prepare a soul for citizenship in the Kingdom.
The drama arises because at any moment an individual can put a stop to this process. Free will means that a person can turn away from the Lord who beckons. We should always be cautious when we see the first sprouts of faith starting to spring up in a person. Of course, this is cause of rejoicing, but it is also a time when the temptations are greatest to turn back to the former way of life (think of the parable of the sower). In a word, the cause of turning down the divine invitation is sin. Every stage of the Christian life requires encouragement, but this is especially proper to the beginning as a person first gets to know Our Lord.
The Redeemer went to Jerusalem to offer the the sacrifice which would redeem the people He loved. Nonetheless, Every moment of His life on earth from the time of the Incarnation was redemptive. Likewise every person whose name is written in the Book of Life has been saved, will be saved, and is being saved.