As we consider this question. We must understand that it is never God's will that people would be raped or that any bad thing will happen to anyone. All the evil in this world is either the works of the devil or the result of sin. While this is in our mind, why does God allow rape to happen anyway?
Rape is a crime and is indeed a sin. Why does God allow sin to do it's work? In reality, God's mind is beyond our grasp. To answer this question we are only going to take what the Bible has revealed to us. But ultimately, it is only God who can give us the exact reason for everything.
Here are 7 possible reasons from the Bible why God allows rape and other evil things to happen today:
To prove the devil wrong. The best illustration for this would be Job. Job is a faithful person (Job 1:1) but he was struck with tragedy. Now Job was not raped (certainly) but he lost his children and his riches and his body was filled with terrible boils. Why? There was a great controversy behind. Satan challenged God. (Job 1:6-12) In simple words the devil said, "Job is faithful to you because you are protecting him. Remove your protection and he will curse you to your face." In the case of Job, God allowed Job to experience great troubles to prove that Satan's accusations are wrong. What was the result? "Then Job arose, and rent his mantle, and shaved his head, and fell down upon the ground, and worshipped, And said, Naked came I out of my mother's womb, and naked shall I return thither: the LORD gave, and the LORD hath taken away; blessed be the name of the LORD. In all this Job sinned not, nor charged God foolishly." (Job 1:20-22) If a faithful person is raped and still remains faithful to God, his/her desecrated body will be replaced with a glorified one when Jesus comes.
We reap what we sow. Galatians 6:7 says, "Be not deceived; God is not mocked: for whatsoever a man soweth, that shall he also reap." To illustrate this point, let us consider a woman who walks the streets barely naked. God bids people to cover themselves properly. 1Timothy 2:9 says, "In like manner also, that women adorn themselves in modest apparel, with shamefacedness and sobriety; not with broided hair, or gold, or pearls, or costly array." If a woman chooses to disobey God by wearing inappropriate clothes and gets raped, she is barely reaping what she sow. We understand that some people calls this victim shaming but the reality is, we are also responsible for our own safety. There is a saying in the field of Chemistry, "Not all chemical reaction can happen without a catalyst."
To turn our eyes to Jesus. Some people will never remember God until tragedy strikes them. The experience of the Israelites would be a good illustration. While the Israelites were traveling from Egypt to Canaan, they begun to speak against God and against Moses. (Numbers 21:4-5) As a result, fiery serpents came biting the people so that some of them died. (Number 21:6) "And the LORD said unto Moses, Make thee a fiery serpent, and set it upon a pole: and it shall come to pass, that every one that is bitten, when he looketh upon it, shall live." (Numbers 21:8) God allowed tragedy to strike Israel so they will come to back to Him.
To bring us to righteousness. Heb 12:11 says, "Now no chastening for the present seemeth to be joyous, but grievous: nevertheless afterward it yieldeth the peaceable fruit of righteousness unto them which are exercised thereby." Mary Magdalen committed evil in the site of God but when she experience chastisement, she found herself at the feet of Jesus.
To purify us. Isaiah 48:10 says, "Behold, I have refined thee, but not with silver; I have chosen thee in the furnace of affliction." Faithful people are not exempted from troubles but every problem that comes to them is a trial and brings about purification.
To strengthen us. 2 Corinthians 4:7 says, "For our light affliction, which is but for a moment, worketh for us a far more exceeding and eternal weight of glory;" A good number of God's most faithful workers today had some of the worst experiences in the past.
To experience the life of Jesus in our flesh. 2 Corinthians 4:11 says, "For we which live are alway delivered unto death for Jesus' sake, that the life also of Jesus might be made manifest in our mortal flesh." Numerous people from all ages had been raped and some even martyred because of their faith nevertheless their experience can't get any worst than the experience of Jesus.
This question is coming from Ken of Bulacan, Philippines.