Reason #1: It's more of a Romance than it is a formalized system of theology (although I think it can actually be formalized and logically defended to a much greater extent that Aulen does).
It is so incredibly easy, when speaking abstractly and analytically of theology, to lose track of the actual Things behind the words and ideas.
But CV doesn't speak in abstract terms, and it doesnt' seek to analyze too closely its various components. Instead, it speaks in imagery and action: Christ descends from heaven disguised as a mortal, to do battle with the devil. He devises a trap and springs it, rescuing his people from the tyrants of Sin and Death: Indeed, he makes Sin and Death his own captives, and makes a mockery of them!
It's action. It's adventure. It's a love story. It's everything good and true and pure that the human soul finds, in bits and pieces, in great literature: indeed, it is what makes great literature great.
Reason #2: Christ "plays by the rules."
In CV, Satan has legal rights to humanity. This likely stems from Hebrews, which states that the devil is the one who "holds the power of death." Reading through the Church Fathers, you see a doctrine in which Satan, by deceiving Adam and Eve into sinning, gains "legal" power of them as sinners.
Of course, this "legal" power stems ultimately from God: Some see Satan as in some sense the executor of God's judgement on sin (See The Lion, The Witch, and the Wardrobe, where the Witch is described by Mr. Beaver as "the Emperor's hangman"), and God is, after all, sovereign (though not necessarily in a Calvinist sense...more on this later). However, there is the sense that however "legal" his possession of humanity might be, he got it through deceit, and he is abusing it.
God could, if he so chose, sweep in under his sovereign power and forcibly liberate humanity from its slavery. He could exert his divine power and simply remove Satan altogether. He could act outside the order he created: That would be his right as God.
But he does not do this. Instead, he sets out to "win" humanity back from within the created order, acting according to the "rules". And there are two ways that CV sees this happening (either as one or the other, or as a combination):
- Christ offers his life as a ransom for humanity, and Satan is eager to make the trade. There is, in a sense, a contract or bargain that is struck between God and Satan, where Christ agrees to die as a ransom for his people.
- However, in killing Christ, Satan overreaches and loses all power. Christ had done nothing to merit death, and when Death (as CV often personalizes it) attempts to strike him down, Death loses all power and authority, as a law which convicts an innocent man will be annulled.
(A careful reader of CS Lewis will notice that BOTH of these themes are present in Lion, Witch, Wardrobe. First, Aslan agrees to give his life for Edmund: But due to the workings of the Deep Magic, when an innocent being is killed, death loses its power, having overstepped its bounds).
Finally (and although this is the main reason, I've left it till last because it has the most potential to be controversial), Reason #3: It presupposes a genuine enmity between God and Satan. Satan is doing things that God genuinely does not want to happen.
That dualism, that sense of real conflict, sits at the heart of Christian theology. A bedrock assumption of the Bible is that there is a thing called Evil, that it is real, that it is really evil, and that it is at odds with God's genuine desires. God really desires a cessation of evil, and he plays no role in its creation. Sin grieves God, and he wars against it, to bring about the end of evil, and the salvation of those under its thrall (us).
But Here's the thing: This sense of enmity and conflict literally cannot exist in Calvinistic theologies, and this is for one very simple reason:
In Calvinism, everything is ultimately as it should be. Everything, including the initial Fall, was not only "allowed" but actually planned, designed, and carried out by God (albeit through secondary causes).
That means that there cannot be the genuine enmity that Christus Victor presupposes. Satan can't be doing anything that God doesn't wish to be done, because Satan only ever does the things he was meant by God to do! It is, at best, a thoroughly one-sided enmity: Satan thinks he is going against God's will, but from God's perspective, it's more like a puppeteer pretending that he is genuinely at odds with one of his marionettes. Or as my friend Danny M said, it's like a child having a pretend war while playing with toy soldiers.
CV cannot exist in a Calvinist theology, because there is no real enemy; There are only various ways and means that God employs to irresistibly bring his predetermined plan to fruition.
There is no real war: There is only God playing with toy soldiers, occasionally knocking some down and making pew-pew noises.
And there is no real victory: Only a cessation of one way in which God brings his inevitable will to pass.
And to that philosophy of puppets and fakery, Christus Victor says "No." The early Church believed what the Bible seems to plainly teach: That Sin and Death are enemies not just of ourselves, but of God. That Satan is an Accuser and a roaring lion, and that God genuinely does not wish for us to be devoured. That Jesus came into the world to tie up the strong man, to plunder his house and set the captives free.
And to that, I say "amen."