This has been sitting around since my power at home went out and I did not expect it coming back tonight... so I must post this: omgwtfBBQ
God is a programmer, Earth is one of his latest simulations. His pride and joy. He programmed Mars earlier, but had to throw it out because of its limitations.
God's developer tools mucked up around 2000 years ago, so he had to call in Jesus to fix it for him, but... it was pretty frustrating for him. So God has lost interest in actively playing with the Earth Simulation afterward, but let it continue running, so it is still simulating on its own.
Since then, every now and then, God's girlfriend decides to mess with the Earth Simulation. She is much kinder on the Sims then God ever was. Sometimes. Every time God catches her messing around with the Earth Simulation, he shoos her away. The Crusades were all her doing if you wanted to know. She punished Europe's continued failure with the Bubonic Plague.
Give him a few thousand more years and he'll come back if he hasn't started on another project.
The Jewish religion is an emergent AI religion. Admittedly, God started with the Jews, but abandoned it early on and rigged up a unique AI God for it, emulating much of his own influential capabilities in the Earth Sim. The Muslim religion uses the same baseline AI God too.