We must understand that not all the things that happen in the world are God's will. The will of God is expressed in His commandments. There are many things happening which are not according to the purpose of God. We must understand what is happening in our time. The things that we see happening in our time are not altogether God's will.
The will of God is revealed through the word of God written for us in the Bible. The commandments of God tell us what God wants to happen in the world. The word of God teaches the will of God. For instance, God says do not commit adultery but people are committing adultery everywhere. Would you say God wants them to commit adultery? No!
Men chose their own way and abandoned the way of God. In doing that, they brought the things that God didn't want to happen into the world. So, the bad things happening in this world are caused by man. Man refused to obey God and choose to do what he wants, that is why there are many evil things in the world.