>>518813007
They want to rule over humanity. They hate God, but they cannot attack him. So then they hate and ruin His favourite creation, humans.

Demons eat loosh (negative human emotional energy). This is their food, they die without this. They asked for the child sacrifices for thousands of years. By having full, centralised control over humanity, they can create more loosh for themselves by causing more abuse, harm, pain, trauma, sadness, depression in the world.