[it was by faith that they of old were called]: Moroni is not referring to the priesthood, though certainly that is involved. There were many who were (and are) called to the priesthood. His reference is to “they of old.” This is a reference to the patriarchs and prophets. The phrase “they of old” indicates the great men of the scriptures, and those men are deemed great because of their revelatory and prophetic relationship with God. Thus it was their existing faith that allowed them to be called as prophets and leaders.