2Co 11:1-3(1) Would to God ye could bear with me a little in my folly: and indeed bear with me.(2) For I am jealous over you with godly jealousy: for I have espoused you to one husband, that I may present you as a chaste virgin to Christ.(3) But I fear, lest by any means, as the serpent beguiled Eve through his subtilty, so your minds should be corrupted from the simplicity that is in Christ.
I understand what Paul is saying in these verses; more now than I did a few years ago. Many people start out believing, and then Satan starts working on their minds and they are deceived and they walk away from what they knew.
Satan does not attack unbelievers. They are no threat to him. It is God's people that he works on. He is trying to destroy God's work. He knows he cannot win, (read the end of the story!), but in bitterness he does all the damage he can while he still can. Just like any jealous and hateful person you know, even if they cannot take what you have, they will still do all they can to damage and hurt.
Satan's best work is to cause people to drift away from God. When people are apart from God, they lose a LOT of blessings, and they do not increase the kingdom of God. So, Satan is able to damage both the person and the kingdom.
We don't have to let it happen! Stand fast in Christ.