He didn’t allow it - He ordained it.
The question is faulty and based on an unscriptural perspective. A high view of man and low view of God’s holiness and justice. Not unexpected from WAPO. The better question is why does God suffer a wicked world at all considering he destroyed it once in the flood? The answer is that the world is still under God’s wrath and will be judged at the appointed time but the good news is that all that God has given to Christ before the foundation of the world and all who trust Christ alone and his atonement for sin will be spared his wrath at judgment.