The Bible says that we have inherited a sin nature from our father Adam. Originally, Adam did not have this nature, but when he sinned it passed to his descendants. Satan was created as a perfect being as well, with the capacity to sin. Our wills want to sin. We don’t want God, naturally. We may know that there is a hole in our lives without God, but we try to fill it with gods of our own making (be they idols, or things like money, fame, etc.,) Only through God’s touch can we even have the capacity for a good nature. Men do good things, due to the image of God that still has its imprint on mankind. But ultimately, they will choose against God unless He intervenes.
Why did God create satan, knowing the choice he would make before He even created him?