I'm an atheist, but let's assume for the sake of argument that a single God exists and that early religions for the most part reflected what God wants from the human race, no matter how heavily distorted the message. A few hundred years after Christ, the status quo would have been threatened and things would have been going badly for the devil...
The religious movements up to that point were fragmented and thus allowed for a good amount of strife and hedonism. The "peaceful" ones like Hinduism and Buddhism weren't really players on a global level, and were contained well because they did not stress proselytism. However, now you have a new player on the court after Christ. Christianity believes in peace as much as they do in rabid proselytism. This new religion has the potential to suffocate the violence and other assorted fun on a global scale. Even worse, it's spreading like wildfire WITHOUT the good part - violence.
What's the prince of darkness to do?
Can't really run a campaign promoting Satanism - no one goes for that even nowadays. How about creating a new fake religion, which will take the most effective points of Christianity and ensue strife for two thousand more years? Let's see, what can we throw in? How about:
1. Proselytism, proselytism, proselytism. You have to convert others no matter what it takes.
2. If you leave the religion, you are sentenced to death. Talk about a good retention plan.
3. An "us and them" mentality - kill the heathens before the heathens kill us.
4. Allow multiple wives for the wealthy, which means a shortage of women for the poor. A young man who can't find a mate is a wonderful candidate for anger and violence.
5. Codify that questioning the religion means death.
6. Constant reinforcement - you must pray 5 times a day so you don't let your mind drift for more than a few hours at a time.
7. Make sure women are considered close to property, that ensures a constant source of contention.
Before anyone accuses me of being anti-Islam, let me cheerfully point out that I am. I hate all religions so I'm an equal opportunity kind of militant...
