One reason why God allows Satan to cause so much evil and damage and suffering on earth, is so that people will thereby turn to God.
Do you realise that if life on this earth had been very comfortable, with no sickness, suffering, poverty, or misery, hardly anyone would have thought about God at all?
Everything that God allows is for a purpose. We read in the Old Testament that when the people of Israel in the wilderness forgot about God, they were suddenly bitten by poisonous snakes. Immediately they turned to God. And God healed them (Numbers 21). Wasn’t it a good thing that those poisonous snakes were there to make those people turn to God?
I heard a story of a businessman who had once been close to God. He drifted away from God, as his business prospered. The elders in his church spoke to him repeatedly and tried to turn him back to the Lord. But he was too occupied with his business. One day a poisonous snake bit the youngest of his three sons, and the child became seriously sick. Even the doctors gave up all hope. Then the father was really worried, and sent for one of the elders of the church to pray for the child. The elder was a wise man. He came and prayed, “Lord, thank You for sending this snake to bite this child – because I could never get this family to think about You at all. But what I could not accomplish in six years, this snake has now done in a moment! Now that they have learnt their lesson, Lord, heal the child. And grant that they will never need any more snakes to remind them of You again.”
There are people who do not think of God until one day they are suddenly taken to a hospital with cancer. Then, all of a sudden they begin to think of God and they turn to Christ and are born again.
Incurable diseases, sicknesses, poverty and many other evils in this world have all been used by God to turn people away from their sins to have an eternal home in heaven. That is how God uses the very things that Satan does to save people from his clutches and save them for all eternity. Thus God makes a fool of Satan again and again.