If Jesus said, literally, father, why have you forsaken me, then why would Xians worship the deity that forsook the one they follow/
Also:
If Jesus did state that on the cross, why would xians worship Jesus, or even follow Jesus, when He was forsaken by the deity they claim to worship as well?
I think first of all it might be pointed out that Jesus
expressing an experience of feeling abandoned by God does not immediately constitute Jesus actually
being abandoned by God, unless you assume a certain view of Jesus which already completely diminishes his humanity, such that he can never give expression to something unless it's "literally" true. But human expressions, human words, are more than informational propositions. They are more than assertions of truth. If Jesus is human (regardless of whether he's "more" than human), it is not immediately clear that the quote should be elevated to an absolute expression of a metaphysical truth.
Having said that, it's interesting that the four gospels all offer somewhat different accounts of the crucifixion. These words appear in Matthew and Mark, but not Luke or John. In the versions where it appears, Jesus says nothing else during the time. In John he says words to the disciples, is thirsty, and declares "it is finished!" In Luke he promises paradise to the robber, asks his Father to forgive the ones crucifying him, and commends his spirit into that same Father's hands. So one answer to your first question could be that the early church, in writing down the gospels, did not consider it be the case that God actually abandoned Jesus.
Beyond that, I think as far as understanding the text, the words that are reported, we could approach them in three ways:
1) If Jesus really said them, how did he understand what he was saying? What does it mean for him in that moment?
2) 2 authors of gospels included these words. How did they understand them? What did they want to convey to their audience by including them?
3) What do they mean to me, now? Which is not necessarily a completely separate question, but could still have a distinct answer
How did Jesus understand his own experience?
Do we even dare to attempt an answer? Can we really know this in a way that can deserve to be called more than pious speculation? Do we run the risk of merely offering an answer designed to satisfy our prior theological convictions? And it's not even just a question that's difficult because it's about Jesus. It seems that to interrogate the very personal experience of anyone in such a situation is delicate. The most obvious answer is that he felt abandoned by God. I wouldn't want to explain away the obvious just to make a certain theology feel more confortable.
At the same time, all the gospels report that Jesus spoke of God as his Father. His Abba, even. This was an unusual way of speaking about God, there is an intimacy that is not common in his culture at that time. They also report Jesus praying with pain and blood in Gethsemene, "take this cup away from me. Nevertheless, not as I will, but as you will". Everything we can possibly know about Jesus' own experience comes filtered through the memories and agendas of his followers. That matters and shouldn't be forgotten, but it does seem to me that this intimacy with the Father that Jesus expressed in the gospels should inform how we might hear these words also. As should the fact that it is a quotation from the Psalms. Without venturing into the theological, I hear it as a cry of pain and suffering and bewilderment that nevertheless finds expression within the very tradition and understanding that it seems to question. Jesus may feel abandoned, but the very act of quoting a psalm to express it is to affirm the importance of that relationship with God as Father that it seems he feel so deeply.
How did the gospel authors understand it? Why did they include it?
It seems clear at least that the authors of Matthew and Mark did not believe that God had truly abandoned Jesus. They report his death occurring simultaneously with the tearing of the veil in the Holy of Holies, an earthquake, open tombs, the darkening sky, all these tumults causing being signs of the importance of what has occurred, and causing the centurion to exclaim "truly this is the Son of God" Whatever significance they gave those words specifically, it's clear it wasn't to agree with the bystanders who thought that if God was truly his Father that he would be saved from the cross. But like John, they seem to have accepted that his kingdom was not of this world. It also seems clear from Matthew's exposition of the roman guards remembering how Jesus was supposed to have said that he would rebuild the temple in 3 days, or the prayer of Gethsemene, that the author understood the death of Jesus as being a necessary thing, ordained by God, a burden taken on freely by Jesus. It seems to me that they hear it as bearing the great weight of this death, it's importance and solemnity. Citing Hebrews, we could conjecture that its very expression of humanity mattered to them, that we have a High Priest who can empathize with our humanity. Really, they don't say anything about the expression directly, so it's only from the immediate context, the phrase from the centurion that "truly this is the son of God" that I think we might infer a little.
How do I hear it? What does it mean for me?
It seems to me that there is something in the ambiguity of the expression, that it despairs and feels lost yet at the same time expresses that confusion with a psalm, within the very context of that intimacy with God -- not only as Father but as Abba. It seems to me that the great difficulty of Christianity and a Christian understanding in the context of modern life is expressed by this ambiguity. There is the problem of evil and suffering, or the difficulties reconciling Christian tradition with the rapid advances in science and technology, changing cultures and morality, questions about faith and the miraculous, and etc. In all of this it seems that we have lost our myths and don't know what to replace them with. The "hiddenness" of God and the uncertain intellectual foundation of faith. The failures of many church structures and organizations. Our own failures. Perhaps it's audacious to compare all that to the experience of death by crucifixion, but the existential angst of it feels similar, at least to me. And yet I also express that struggle with the very symbols that the struggle calls into question, and that is also meaningful to me.
Where does this experience go? I prefer to leave it open. What I take away from it is the very human experience of contingency, of humility, of not having every answer, not knowing everything, not even needing to know everything. I experience God and that experience is profound, even though at times I'm at a loss to understand what it means or how it all fits together. It seems to me to be something constitutive of being human.