The devil was kicked out of heaven for making one mistake, so he suffered lifelong consequences and turned to the dark side permanently.. What if he now spends every waking moment of his life trying to get others to sin so they too wont be allowed in heaven and that way he wont be so lonely? maybe hes just trying to fix whatever inside of him is broken.
Its kind of like drugs Addicts in a way. No normal person needs to get high. you start out needing to fix something in your life that's not working, eventually your a slave to the drug in hopes it will fix you.
Nice try.