Well, someone had to take it on. The most sincerely and insincerely asked theological question of all time. Here goes.
There are a lot questions about the afterlife, namely, what will heaven be like? The scriptures give us some clues but when measured against the fact that Christianity is about the promise of life eternal with God there is very little to go on. One might think that there would be chapters written on the specifics of heaven. My point here is that God decided to tell us tidbits in light of the absolute and overwhelming beauty heaven must entail. What we can be assured of is it is a place and Christians will be going there because he said so. He has given us his word.
Before the Fall, God planted a garden in Eden; where he formed many trees, trees which that "were pleasing to the eye and good for food." Among the trees was one called "the Tree of Life" and one termed the "Tree of Good and Evil" . God said "You are free to eat from every tree in the garden; but you must not eat from the tree of the knowledge of good and evil, for when you eat of it you will surely die." We all know that Eve and Adam each partook of the fruit from the tree of good and evil.
Now I am going to skip over a ton of details and theology to get to my point, which is that God keeps his Word. At the moment they partook they began the process of death. Before the Fall, it appears that Adam was a vegetarian and that there is no mention of the death of anything, so when God told Adam he would die if he disobeyed we do not know what Adam understood by that. Did God have a sit down with Adam to explain the foreign concept of death? We do not know. We do know that no human being had ever died before. God laid down the law, Adam broke it and God kept his word as he always does. So all of today's free will advocates that believe all choices are in your hands and that what you do affects the order of the universe here is your verse. Adam had free will, used it, and brought death and destruction and suffering into the world. Isn't free will the greatest?
So this is why God allows death and destruction in the world, because he is a God of his word and allowed the ramifications of Adam's choice to enter the world. He did not violate Adam's free will. He did not give a day and an hour when death would end on this earth, and so it goes on. In a sense we got what we asked for. To this day we demand free will because after all God doesn't want a bunch of robots does he? What about our free will then? You see Adam's choice killed our free will because we became spiritually dead and enslaved to the serpent now that we knew good and evil. That is what sin does- it begins a chain reaction of pain destruction in it's path. It was within a short time that murder in the first family erupted after all. ..So you see "we" , as human beings, had free will but lost it with the bite of the fruit when sin entered our race and we began to die. Paul says clearly that before God made us alive in Christ we were slaves to sin, and slaves do not have free will: "...the sinful mind is hostile to God. It does not submit to God's law, nor can it do so. Rom. 8:7
So just as God didn't tell us much about heaven in scripture and yet we trust it will be more than we can hope for, so he told Adam little about death and let him experience the results of his actions which I am certain was more than he could have ever imagined. And so God has let the course of human beings run until that day when he enters our world and conquers once and for all the ramifications of our collective, fallen, choices .
Unless you have a high view of the fall as outlined in Genesis, namely that it actually happened, you will always be at a loss to understand the horrors and sadness of this world. But if you trust this is what happened that God allowed ramifications of Adam's free will to reign - than it begins to make sense.
Immediately after the Fall, God comforts the first couple with the promise of the one that will come from her seed that will destroy the head of the serpent whilst suffering an injury to his heal. How exquisite in love and detail. We know now that the Romans did not nail the foot of the criminal to the cross but rather the heel. (Gen 3:15). God cursed the Serpent but blessed our parents with the promise of one that would make it all right again:
"For if, by the trespass of the one man, death reigned through that one man, how much more will those who receive God's abundant provision of grace and of the gift of righteousness reign in life through the one man, Jesus Christ." Rom. 5:17