Trees and anvils have no free will and thus no intent. There is no moral implication in a mere accident.
Disney cartoon or Eden?
I cannot guess God's motives for allowing evil save that if God believes evil should be allowed to exist and be practiced then who are we to say it should not? God would certainly have created us with the capacity for gross injustices, knowing full well what we would do to each other. From whatever point of view I take, I can find no excuse to love a parent who would not save her son from a long, slow, torturous death should it be in her power to do so. Our laws demand as much, our sense of social duty expressed in law and morality (Christian morality at that!) demands as such too.
If God were a parent he would have seen his creation taken from him and he imprisoned for negligent homicide and gross indifference to human suffering ages ago.
If God were a parent and acted to save us from the evil we perpetrate against each other then would not God be acting as responsibly as even we, his imperfect creations, would? A parent may love a psychopathic child yet still prevent him from doing harm to others. Does not God, who willed us to be, need to do as much? For if we exist because of the will of God, does he not then owe us his protection? Otherwise we then suffer at the pleasure of God and that is a perverse thought. That is why the will of the evil always trumps the will of the innocent or the good. In the Judeo-Christian theology it's, "free will," to toss a child into a burning oven to burn to death despite the fact I daresay that child wills with all his or her might that it not be so. Evil triumphs! A man in Missouri captured an 18 year old boy, chained him to the ceiling and castrated him of penis and testicles while the boy bled to death for hours begging to be let go until life left him. Where is God then? Who among us who had the power to stop such a thing would not do so? That boy willed with all his might, likely even begged God to stop his wretched death, yet God did nothing but let him suffer until his life bled out of him in unimaginable pain.
Where there is no hope of rescue, where good men do not even know that evil is taking place, where is the moral lesson? How does it serve us or God? What purpose does such suffering serve? None! For there is no Disneyland about a child being tortured to death, a woman gang-raped or stoned to death, or young men being tortured and then vivisected without anesthesia in such a manner that they stay alive with their flesh splayed open and organs cut and proved for HOURS on end only to die crying out for death itself? Left merciless without any hope of rescue, any righteous ear to hear and fight for them save ONLY God?
Given that or Disneyland, I'd prefer Disneyland and were I wager you ask the victims of such atrocities I daresay they'd rather be in Disneyland too.
Remember that the inhabitants of Eden knew nothing other than Eden and were perfectly content. If God made us curious then that's his own fault and we suffer for that.
No, I don't think you will ever find a truly satisfying answer to that most profound of questions? But let me ask you what the world would be like if anytime a tree fell on you, it would magically vaporize before it hit you. Or if we were all lobotomized to the point where we were incapable of harming each other? How could we operate in the medium of the world where objects changed form and nature frequently and vigorously so as to avoid causing anyone any kind of harm or suffering? This is the world as Disney cartoon.
If you were a God of a world such as this, would you shut it down because of the potential for suffering? Would you turn it into a cartoon world where anvils fall on people's heads and don't really hurt them? Would you give the inhabitants unlimited resources so they wouldn't have to compete with each other for them?
What you might do instead is to run a 4000 year viral marketing campaign to influence the belief system in the world's inhabitants so as to change their behavior without coercion. In that way they would be your hands and feet in trying to mitigate injustice, misery, and suffering in the world.