My answer is that they fail to take account of the primary assumptions of God being creator, wholly-good and our wholly-loving Father.
It seems clear to me that many or most Christians - past and present - do not really believe these assumptions - becausse their world picture is grossly incompatible with them. But why do they not (really) believe the primary assumptions?
In the first place such assumptions can only be known by individuals, and by direct-knowledge, intuition, faith. There are no real 'arguments', no 'evidence' to support the idea that God is creator and loving Father - either you know this, or you don't.
Perhaps you don't know it because you have never asked the question - or you may know it but doubt the validity of this kind of knowledge (and need to alter your metaphysical understanding) ... Many billions of religious people who believe in a creator-God have not been able to feel or acknowledge that God is truly a personage - but instead they have an abstract view of God (as like a 'force' or described by abstract properties such as 'omnipotence'). For them God is a creator of total power, but they don't really know anything about God, cannot be sure of his nature and motivations - and therefore cannot infer anything about the world. They might believe in a monstrously horrific human situation - and yet not be sure that this is incompatible with a creator that is good, loving, our Father because the regard goodness, lovingness and Fatherhood as merely abstract metaphors; un-interpretable and not directly applicable to 'real life'.
Others believe in God's complete goodness, but their God not the creator - so their God has very limited power to set-up the world. The world might be set-up as a horrible place of torment, maybe even made or run by evil entities...
However, my point here is that Christians (supposedly) personally, fundamentally believe that God is wholly good, the creator and our Father (that is, intimately concerned with us, his children; and concerned that we grow up and grow up well). All of these.
And yet in actuality many/ most of these Christians have a concept of the human condition as one that ought to be lived in constant and dread-full awareness of the proximity of eternal torment in Hell as the natural, just and default end to mortal life. (Their primary argument is Believe or else. It is the fear of 'or else' which compels belief, not the positive consequences of Christianity. For them; Christ came to save us from a world set-up such that we were destined for eternal torture - that is the 'good' news.)
All this is bound up with notions of The Fall and Original Sin which are abstracted-from/ Imputed to the Bible - yet are far from clear in the Gospels. Why have they become so central, so indisputable, to so many people?
The short answer is that not many people have ever really believed that God is our good, creator Father.
Think about our own earthly Father or Mother - as a child, if we believe they are good, we trust them; and we interpret their actions (observed and imputed) in that light - in the light of knowing that they love us.
We don't let any specific action, or their average of actions, or anything we read, or anything which 'other people' say, have any influence AT ALL on the knowledge of the fact that they love us.
So the mass of Christians do not assume the loving goodness of God, they de facto test it. For example, they test the gooodness of God by reading the Bible, or Church pronouncements. This is equivalent to a child starting each day agnostic as to the love of his parents, and weighing all their actions and statements about them to decide - day by day, moment by moment - whether his parents really do love him - or not.
The fact is, such a child could never reach a conclusion, because it is formally impossible to test whether somebody loves you or does not; whether they are good or not. These are matters of assumption - hence of direct knowledge (or if there is no direct knowledge then they are not known).
This is the craziness of trying to learn about the nature of God by reading the Bible, or reading the Church Fathers, or reading the documents of the church. By doing so we have already, implicitly, mistrusted God, put God on trial; have decided that God is NOT (not really ) our Heavenly Father and creator.
We are relying upon our fallible interpretation of fallible texts for our understanding of the fundamental nature of God and reality! - little wonder that nothing or nonsense are the typical consequences!
Little surprise that - at the end of such - such common - activities, people end up with a view of Christianity that is - at its most basic level - inverted. To focus on Hell instead of Heaven, to impute a Fall and original sin as the primary and focal points of the human condition... this is crazy stuff to anyone who really believes that God the creator set-up this world and that God loves us as a Heavenly Father and is wholly good - because such a one would obviously not have made such a world.