He allows Himself to be arrested and crucified. But the grave can never hold the Son of God. Within three days He is once again touching the lives of His followers. In harmony with God's plan, the Lord leaves His followers to build and nurture His kingdom, His body, the church. The Master leaves behind a kingdom which is stronger than death itself.
Nothing can conquer the kingdom.
But there is no promise that it would never suffer damage. There is no promise that apostasy would not occur. There is no promise that the Devil would be unable to lead many astray. In fact, the New Testament warns against apostasy. Nearly every book in the New Testament contains a caution against false teachers.