There was only one Jesus of Nazareth, and he was only executed once, and the mission of this single man and his single death formed the basis of the jewish cult which followed him and eventually became christianity.
There were many crucifixions in Roman and other cultures of human beings. Ever hear of the Passion Plays?
The Crucifixion of Yeshua at first was for crimes against the Roman state (sedition and treason), blasphemy against Jewish law, and, from his followers point of view, as a martyr for their religious cause. But it was not until later that the theme of the shedding of divine blood for the express purpose of absolution of Sin came into being. However, the elements for that theme were already in place, from previous pagan myths and religious beliefs.
If it had been true that his Crucifixion was for the express purpose of absolution of Sin, he would not have asked his Father for the unconditional forgiveness of his murderers. In fact, he did not ask forgiveness for their sin at all, but for their ignorance, and that is a Buddhist idea. Modern Christianity always demands first contrition and then repentance before forgiveness can be granted. Yeshua demanded neither, and for the most heinous of crimes. The fact remains that, the Crucifixion was a bloody punishment which, at the time, had zero spiritual significance. It became, however, the crucial core of all Christianity, as it was by the shedding of divine blood that Sin was washed away. The idea of the Resurrection was only important insofar as it "proved" that Jesus was divine.
Without SIN, Christianity would cease to exist. There would be no need for Jesus to have come to Earth to die on a cross as payment for the Original Sin of Adam and Eve. It was the Crucifixion that paid that debt for all mankind and re-opened the Gates of Paradise, as well as freed souls from Limbo, where Jesus is reported to have spent some time after his death before ascending into Paradise. Without SIN, there would be no need for Repentance, Forgiveness, Heaven or Hell.
The idea of animal sacrifice, yes. But not crucifixion, and not human sacrifice.
It does not matter. Both animal and human sacrifice served the same purpose: the absolution, via of a scapegoat, of sin and guilt. Yes human sacrifice as a god-man because all previous sacrificial hosts were imperfect in the eyes of God, and therefore unacceptable. Only God himself was the perfect host, unblemished and pure. What is important is that there had to be a sacrifice at all, and that is a pagan idea. A mature spiritual approach would be unconditional forgiveness of sin without a price tag. Try to understand, that, one can forgive even the most heinous of crimes because their basis is ignorance. One forgives ignorance, not the sin itself. And that is exactly what Jesus (Yeshua) did, and the understanding of this fact is most crucial.
C. S. Lewis, one of the greatest christian apologists of the 20th century, converted to christianity specifically because he believed that Jesus and Christianity represented perfection of an idea that was universal, not because of anything unique.
CS Lewis was'nt much of a thinker, not really.
Christianity was not, however, universal, as you state. If anything, it was exclusivist, for it accepted only a few worthies.
'Many are called but few are chosen", and
"Enter through the narrow gate; for the gate is wide and the road broad that leads to destruction, and those who enter through it are many. How narrow the gate and constricted the road that leads to life. And those who find it are few" (Matthew 7:13-14).
In order to be saved, the Christian God's Love is Conditional:
"No man comes to the Father [ie; heaven] except through me" even though the price of entry into heaven supposedly was already completely paid for via of the Crucifixion. Apparently it was not.
Now, Buddhism is truly Universal. It embraces all of life, right now, just as it exists, warts and all. It does not discriminate. According to the Dharma, there are literally tens of thousands of paths to Enlightenment, not just one narrow gate. In fact, in Zen, for example, the gate is gateless.