The true church, as has been said, has always been under satanic attack. And even in times of horrific persecution, it has had the strength to survive because of its 'secret' weapon - the known cure for mankind, which is deification, whereby the old nature is done away with and man can achieve what he was made for - union with Christ, as the temple of God and that a man who is walking in the Spirit, has an ear with God due to his pure heart and clean hands. No foe is strong enough for that.
However, nowadays, the enemy is within the church, and this doctrine has been done away with or replaced with a false one which says sanctification is gradual. Hint! You never get there!
It is the reason why satan has been able to overcome the true church.