Now, that's an angle I haven't considered before. So, man's deceitful nature is just QUALITY CONTROL to cull the defective units in his humankind manufacturing process. I guess quality control is important, but I wouldn't expect a perfect creator to need quality control.
Lately I stumbled upon some videos of a Father who performs exorcisms on possessed people, he had some very interesting things to say about demons (who are all fallen angels) and the devil himself who has encountered in several possessions.
What I gathered from this father is this:
Every angel was created for a specific task. For example one demon told him he was created to protect the trees. Most answer that they were created to prepare the way for the Lady (Queen Mary).
All the demons universally hate Mary the most, and it is usually her presence that finally drives them out.
The devil is manifested into three distinct personalities:
Satan - the inversion of the Father. He is the Father of Lies.
Lucifer - the inversion of Christ. Lucifer’s name means “Light from Light”.
Beelzebub - the inversion of the Holy Spirit. He is the demon of fear.
It is assumed God cursed the devil in this way because the devil wanted to be God.
But what made the devil rebel in the first place?
When he saw that Mary was the perfect reflection of God. Her (inner) beauty and humility and self sacrifice was so much greater than Lucifer’s, and he became jealous of that. He couldn’t stand that a human was more than him.
All the demons are extremely jealous of humans. They want us all to suffer in their agony, by taking away our focus in God. “Anything but God”, is their focus.
Don’t know that any of that can answer “why” God allowed such evil. These angels were given a responsibility, and they failed at it. They wanted a “lesser good” over God.
When Adam and Eve ate the fruit, they seeded that evil into themselves and all their descendants. Perhaps God gave us this challenge to see if we can overcome it.