A dog was created to be a dog, a fly was created to be a fly, demons were created to be demons; its what they are.
They are NOT doing what they do to gain advantage, they are doing it because its all they know to do. Something superior made them like that.
Horse-feathers! Demons were NOT created to be demons. Every intelligent being that God made was given the privilege of FREE WILL. Certain angels that had been good decided to leave heaven and come down to Earth to have sex with human women. When they chose to rebel, they BECAME demons.
"The sons of God [angels] saw that the daughters of men were beautiful; and they took wives for themselves, whomever they chose." (Genesis 6:2, NASB)
Jesus was made alive in the spirit, "in which also he went and made proclamation to the spirits [the demons] now in prison, who once
were disobedient...in the days of Noah, during the construction of the ark." (I Peter 3:19,20, NASB)
"For if God
did not spare angels when they sinned, but cast them into [Tartarus] and committed them to pits of darkness, reserved for judgment; and did not spare the ancient world, but preserved Noah...with 7 others, when He brought a flood upon the world of the ungodly...." (2 Peter 2:4,5, NASB)
"And
angels who did not keep their own domain, but abandoned their proper abode, He has kept in eternal bonds under darkness for the judgment of the great day." (Jude 6, NASB)
Fallen angels. Demons.