It was several years ago that commenter WmJas pointed-out that the Old Testament underworld after death - Sheol (much the same in its characteristics as the Hades of Greek religion) which was the destination for all spirits/ souls after death (the good as well as the bad) - was replaced in the New Testament with a much more polarized distinction of Heaven or Hell: Heaven being vastly better than Sheol, but Hell depicted as vastly worse.
Sheol is apparently a shadowy world inhabited be witless, demented spirits/ souls who have forgotten (or cannot hold onto their own identity (presumably, spirits maimed by having been torn apart from their bodies); whereas Hell is some kind of a place of torment.
This - on the face of it - is a rather ambiguous benefit for Jesus to have brought; and seems initially hard to square with the way that a loving father would organize things for his beloved children.
But this interpretation is, I believe, a consequence of our stubborn refusal to acknowledge that Men have agency, or 'free will', and God either will not or (I would say) cannot compel any Man to choose his ultimate destiny.
My understanding is that Sheol was merely a temporary holding-place awaiting the advent of Christ (and not experienced as having any duration by the souls who dwelt there); and we can interpret the Atonement of Jesus Christ as having led to a situation where all souls were brought out of Sheol and each Man was able to choose his own destiny.
To understand Christianity (or indeed anything) in this mortal life, we need to know what it is for; and my assumption is that the whole of creation was made by God (in a nutshell) so that some Men (as many as possible) could advance to deity and join The Father and The Son (and Heavenly Mother) in a loving society.
Men are made a spirit children, and incarnated as mortal children - but the point is that we are immature, extremely immature - but our destiny (if we choose it) is to mature towards greater and greater divinity.
Mortal life is designed so that 1. Men can be incarnated and have a body. And 2. Men can have experiences, make choices - including errors, and being to mature such as to make spiritual progress.
So, Jesus Christ made it such that the discarnate spirits from Sheol, and every other Man from then onwards, would be resurrected; and then, by his 'taking away the sins of the world', made it possible for Men to choose their eternal destination.
In sum, I am saying that since Christ (but not before then) Men have been able to choose Hell.
Now, it seems strange that anybody would choose Hell; and most Christians through history have regarded Hell as either the default (from which some, maybe only a few, are rescued by Christ) - but this equates Hell with Sheol which seems false.
Or, they have regarded Hell as a punishment place where those Men are sent who are wicked - whether they like it or not - and are tormented forever. Or at least for those Men who fail to keep to acceptable behaviour. But this set-up seems impossible for a loving God - no loving parent would want this for his children; and when God is envisaged this way He seems worse than some Men.
My assumption, therefore, is that Men get what they really want - and therefore Hell should be regarded as one of the things that Men want and choose for themselves - among various other imaginable alternatives, which are often seen as eternal destinations in other world religions.
Hell is to do with Sin - therefore we need to consider how can Sin be conceptualized?
One way is to consider Sin is that all Men are at least somewhat (and some men are very) prone to choose and do what is short-term, pleasurable, pain-avoiding and in a word expedient - rather than what leads to joyousness in an eternal time-frame. This applies to choices during mortal life, and it would presumably also apply to choices concerning destination after death in those who have followed a life of accumulating sin.
The point is that short-term expedient sin sabotages what is best for long-term joyous spiritual progression.
Well, part of the work of Christ was to expunge this accumulation of sin, and allow a fresh choice of destination.
(I will leave aside whether this choice of destination is permanent - but I cannot see why permanence would be enforced: I think the tendency to permanence in long-term destination is due to the self-reinforcing nature of choices, rather than being due to God preventing any resurrected soul from changing his mind.)
From what we know of men and women in the world today, we can see that not everybody want to dwell in Heaven. And, by and large, people will be given what they want - and those who don't want Heaven but instead want something else will have it.
Heaven (a variety of Heavens, in fact) is the destination of choice for those who want to live in loving relationships with their (perhaps several, overlapping) families and loved ones. The highest heaven is for those who wish to become mature, deified 'adults' - and dwell in contact with deity; and lower heavens for those who want to stay as children, or do not want to grow-up towards divinity - or, at least, not yet.
For example, some people do not want to grow-up - but prefer to remain as (immature) children of God. They are allowed to remain as children (maybe they can change their minds again later?).
If you want to lose consciousness, to lose the sense of self, to cease to be aware - to be-absorbed back into divinity, living in a perpetual present of bliss (i.e. the state of Nirvana) then that is allowed.
Perhaps the commonest desire (or belief) among modern Western people is that when they die they will be utterly unconscious - not in Nirvana but simply the extinction of all awareness, as if deeply anaesthetized. If they really want this, that is what they will get.
(Although maybe a merciful God will awaken then form time to time, to see if they want to change their minds? But if they have been utterly unconscious, it is hard to imagine what could happen to make them change their minds...)
Many modern people seem to dislike their birth families, and do not wish to have their own families; they seem not to want to live in a web of loving and responsible relationships - well such people would not want to live in Heaven. What such people seem to want is some kind of shallow, serial, mutually-exploitative (or 'reciprocal') relationships based upon immediate pleasure. I can imagine an after-death world where such people might be allowed to live this kind of life.
This would correspond to the Paradise which is the aimed-at state for some religions; in which the after-life is envisaged as a perfected form of sensuous (indeed sensual) earthly life - a life of pleasure rather than joy; a human-level life, minus the physical suffering. Life as a cycle, without progression, each day much like the one before - pleasant, but going-nowhere.
The problem is that exploitation is seldom equal - one gets more than the other, some people tend to give more than they get - would they be happy with this in the long-run? Is such a system sustainable? This contrasts with love, which enhances both parties; and is sustainable for that reason. But there are some social circles on earth - for example among hyper-promiscuous people - which seem to be based on mutual exploitation, novelty and rotation of personnel. If that is what people want - presumably some provision is made for them.
The problem is those who want to impose their will upon others, to exploit them unilaterally and selfishly - habitual murderers, rapists, torturers, con-men, gold-diggers, psychopaths and the like. Now, clearly such people cannot be supplied with the unwilling victims that they crave - however, they utterly reject loving and responsible relationships of any kind. The question is whether such individuals are prepared to acknowledge their objective wrongness, and repent their wicked desire to exploit and impose?
If such individuals will give-up all claim to have what has been their primary desire through life; then they will not go to Hell because Christ has made repentance wholly effectual; but if they will not give-up their core sin, then they will prefer solitude and the torment of perpetual frustration to being cleansed of that sin.
And if that scenario of chosen Hell seems implausible to you - it does not seem implausible to me; since I have seen individuals in an analogous situation in human life - living utterly miserable lives due to their choices, yet refusing always to repent these choices and repelling all chances at loving society; indeed loathing and despising and wanting to make-suffer those who live in loving society.
In sum, all after-death states including Hell can be seen as a loving Father giving his children what they want - so long as this does not infringe the consent of his other children. And this explains why Christ brought Hell, as well as Heaven.