1 Peter 1:24-25

For all flesh is like grass and all its glory like the flower of the grass; the grass withers and the flower falls off, but the word of the Lord endures forever. And this is the word that was proclaimed to you.

It is because "the word of the Lord endures forever" (NKJV) that there continues to be believers on this earth. From the time of Jesus Christ, His disciples, and others who believed; through war, hardship, kingdoms rising and falling, and the world changing in almost every way - belief in Christ remains. Every believer in Christ has been filled with the Holy Spirit of God, and the same good news comes to us that came to the disciples - "Repent, for the kingdom of heaven is at hand!" (Matt 3:2 NKJV) Forgiveness and salvation have come in Christ Jesus! The word of the Lord endures forever!