From here to the end of the page the register is catechesis — the Church teaching its own faith, not a historical description.
Why he came
The Church teaches that humanity became separated from God — not merely by a legal debt, but by a wound in its nature: death became its end and corruption its portion. Healing could not come from outside, for what God did not take up, he did not heal.
So the Son of God came and took our nature whole, entering the entirety of our life, death included, in order to carry it through from within. This is why the Fathers of the East say salvation is not an acquittal in a court but the healing of a sick nature, and a share in the life of God.
The Cross and the Passover
Christ did not die at any time of year, but at Passover. That is not a detail of timing; it is the meaning.
In Exodus a lamb is slaughtered for each household and its blood put on the doorposts, and death passes over that house. Hence the name of the feast: *Pesach*, a passing over. And it is a feast of liberation: by blood death passed by, and by that passing the people came out of slavery.
The New Testament reads the Cross in exactly this frame. John the Baptist says, “Behold the Lamb of God.” Paul says, “Christ our Passover has been sacrificed for us.” And John places the crucifixion at the hour the Passover lambs were being slaughtered in the Temple, citing the Passover command itself: “You shall not break any of its bones.”
The sense is one and the same: blood by which death passes over, and a passing out of slavery into freedom — and out of death into life.
Note
It should be said that the Gospels do not agree on the timing: John places the crucifixion on the day of Preparation, before the Passover meal, while the other three make the Last Supper the Passover meal itself. The difficulty is old and much discussed, with several proposed resolutions. The link to the Passover lamb as set out above rests on John's sequence.
The Temple and the sacrifice
Sacrifice in the Temple was by its nature repeated: daily, and yearly, with the high priest entering the Holy of Holies once a year carrying blood that was not his own.
The whole argument of the Letter to the Hebrews rests on this: what must be repeated is not yet complete, and Christ entered “once for all” with his own blood, being both priest and sacrifice. This is why his sacrifice is not repeated — in the Eastern tradition the Eucharist is not a new sacrifice but the presence of the one sacrifice.
The Gospels record that the veil of the Temple was torn from top to bottom at the hour of his death. The Church reads in this that the way into the Holy of Holies is no longer curtained off, nor confined to one priest on one day.
The year 70, and after
In AD 70 the Romans destroyed the Temple; the sacrificial system stopped and has never resumed. The date of the Letter to the Hebrews is disputed — many place it before 70, since it speaks of the sacrifices as though they were still being offered — and Christian tradition reads in the proximity that what the Temple signified had reached its fulfilment in Christ, leaving the sign no further work to do.
And why the Cross alone is not enough
Had it ended in death, the Cross would be sad news, not good news. The Church does not preach a death only, but a death in which death itself was defeated.
This is why Christian Pascha — the feast of the Resurrection — is the greatest feast of the year in all the churches of the East, not Good Friday. What the East sings on the night of the Resurrection is not “we are forgiven” but “Christ is risen from the dead, and by death he has trampled down death.”