Why does error have a free rein and why does God allow the wicked to disturb the existence of so many people?
First of all, before trying to understand, we need to put ourselves in front of the incomprehensible wisdom of God. One who is firmly anchored in God does not suffer any loss, even if attacked by a thousand waves and a thousand storms. On the contrary, he emerges stronger.
There is a reason, however, which I can venture to suggest.
In the first place, scandals are permitted so that the rewards of the righteous may not be diminished. That is why God said to Job: “Do you not understand that I have treated you in this fashion so that righteousness may be made manifest?” [Job 40:8]
But there is a another reason why the wicked are left at large: so that they may not be deprived of the advantages of conversion from their evil ways, which certainly could not happen if they had been rendered incapable of doing evil. In this way,
You may speak to me about those who have been scandalized. Well and good. But I then speak to you about those who have benefited from the scandal by winning glory, and I repeat my point: the existence of careless and lazy people would not justify leaving in a state of inferiority keen and wide-awake people who are capable of richly deserving their eternal recompense. A great wrong would be done to them if they were not given the chance to strive.
(SC 79, pp 183ff.)