Christ told us what God is up to in parables. Like a farmer, God is growing a crop. Evil people are weeds mixed in with the crop, which is made up of good people who have repented and are producing good fruit. It’s self evident that this world is part of God’s plan, that it’s a necessary part of producing the crop that God wants. Otherwise, God would end the world now or would have never created it in the first place.
This is what is revealed to me. God wants a certain type of people, and God’s people are often strengthened by adversity. Think of the difference between tomatoes grown in a hot house and those grown in a garden exposed to the environment. Don’t garden tomatoes taste better? It’s vitally important to get right with God before the harvest, so that one is good fruit and not chaff.
I don’t disagree with you in general. The question is, why is it necessary, and that goes to heart of what he’s asking. As I said, the real question to ask is, why did God decide to create at all, and that is something no one can answer...
Adversity never strengthens a believer in fellowship with God through faith in Christ, but adversity, which is inevitable, may be used as a testing of believers. When we persevere through faith in Christ, then we pass another test and by our momentum in Him, continue to walk the walk.