Does the small number of believers contradict the fact that Islam is the fastest-growing religion?

First: Truth is not tied to the number of followers, whether few or many. Rather, truth is often found with the few and the weak, because truth is heavy upon the souls of those who pursue worldly interests. The fear for Muslims is not from their small numbers, but from their weakness, their love for this world, and their aversion to death.

Second: The reasons for the spread of Islam are numerous, among them: that Allah has guaranteed its preservation and triumph, that it is an easy religion consistent with human nature (fitra), and that it encompasses lofty morals and values which indicate that it is a divine, رباني (Rabbani) religion.