Gerald Bray in God is Love has an interesting understanding of the problem of evil: Evil exists because God is merciful. This sounds counter-intuitive at first, but the argument is sound:
Logic and justice demand the appropriate punishment, but God’s love and mercy are greater than they are. In spite of everything his rebellious creatures have done and everything they so richly deserve, God has reached out to them and allowed and allowed them to remain in existence as a sign of his great love for them and of their continuing importance to him as beings he has made and over he he remains fully sovereign.
God is Love, p. 353. So we when we look to the cross, we must realize that it is the sheer mercy and grace of God that Pilate continued to exist and the soldiers were not instantly judged for their blasphemy. It is mercy and grace that the wood persisted and the nails could do their damage.
Bray pushes back and sees a greater wonder:
The preservation of Satan and his angels, and the limited but still significant authority given to them, is the great mystery of the world. If God had eliminated them after their revolt, there would be no problem of evil now because they would have been able to tempt Adam and Eve to fall away. The spiritual warfare in which they are engaged would not exist and the human race would presumably be fulfilling its God-ordained purpose in a world that did not know the power of evil. But this paradise was not to be. By allowing Satan to survive, God acquiesced in a situation in which a force opposed to him would hold sway over an important part of his created universe, and would hold sway over an important part of his created universe, and would be free to tempt the first human into following him. Why did God do this?
Ibid. Why indeed?