I know it's fun making the devil seem good, but no bro don't fuck people's heads up like that.

The devil did it because he could, because there is nothing else better to do in a universe that is tailored to experience and in reality has no good or bad, just is. So, he took advantage of our situation beyond the normal means of doing so, creating popular religion to worship himself (biggest trick the devil pulled off is convincing you "god" and the devil are different, they are one in the same in terms of popular religion).