for God doth know that in the day of your eating of it—your eyes have been opened, and ye have been as God, knowing good and evil. - Genesis 3:5 YLT
Satan successfully deceived Eve and by that act did Adam disobey and introduce sin into the world. It is a disposition that every human being is born with: A disposition to usurp God's singular prerogative to distinguish between good and evil. Atheism
Atheism is nothing more than the ripened fruit of that fallen disposition of flesh.
If the Son of God had not lived, died, and risen there would be no flesh saved. If the Spirit of God were not at work in the world convincing of sin there would be no flesh saved. If the Word of God had not been written and safeguarded down through the millennia there would be no flesh saved.
MostThe Gospel is the power of God for the salvation of those who will believe. Most if not all of Satan's energy and attention is bent on interfering with thethis work of salvation. Lost An atheist is no more or less lost than any other person who is not saved by grace through faith in the Lord Jesus Christ.
Humanity is already predisposed to reject God. Whether lost humanity manifests it's condition through atheism, false worship, or indifference; lost humanity is already lost and cultivating atheism (or anything else contrary to God) is probably best accomplished by opposing the Lord's work on behalf of believers.