Evil started with the pride and arrogance of Lucifer. He got one-third of all the angels to go to hell with him. He and his minions work hard for company. I assume that every soul he wins justifies his evil. Who knows. He hates his creator.
Keep in mind:
Angels outnumber demons 2 to 1.
How did man fall?
By eating fruit from the tree of knowledge of good and evil.
Sin has now been redeemed at the Cross, once and for all.
We are born with souls which are still condemned, but through faith in Christ may be forgiven.
We still suffer in our thinking, with the knowledge of good and evil. We are tempted to then judge good and evil. The real solution is to remain in fellowship with God, the same way Christ remained in fellowship on the way to the Cross.
Many different types of distraction and evil were cast his way in an attempt to divert His thinking from the fulfillment of the Plan of the Father, to instead refocus upon good or evil. Instead, He remained faithful through the Cross.
Sin has been settled in regards to our relationship with God. Good and evil have not been so settled as they must be resolved in time. Be careful not to focus on human good or human evil as a counterfeit substitute for our life in Christ by His Providence. It’s the same fallen temptation used in the Garden.