The theory was simple.
1. Teach a person about God.
2. Belief and fear of God will prevent the person from doing evil, committing crimes...ect.
So...
Why didnt it work?
Christian countries have about as much crime as anyone else.
Japan has much lower crime rate than USA, despite USA being very religious and Japan being very non-religious.
Atheists in USA make 3% of the total population, but only 0.1% of the prison population.
It seems that religion does nothing to prevent crime.
Why is this so?
One theory is that criminals believe that what they did is what God wanted them to do.
It wouldnt be the first time someone uses religion to justify a crime. People justified wars with religion, so justifying crimes with religion is even easier.
For example, if your wife was cheating on you, she would be committing adultery. Therefore, religion can even be a reason for committing a crime, since adultery is punishable in the Bible.
I remember the story of a priest who raped a boy, saying he was trying to cure him of homosexuality.
So apparently, religion is no obstacle whatsoever to committing a crime.
Another theory is that religion is a form of child abuse, and children exposed to religion at early age are more likely to become violent.
Since Christianity is a very violent religion, teaching children that there is a place where people burn alive, it seems obvious that it has no positive impact on mental development of a child.
In fact, you are teaching a child that they must worship a literal psychopath.