The preaching of Islam started over some 1400 years ago in the region of Saudi Arabia, as at first there were very less number of believers but it then drastically decreased due to the reason that people were convinced that its a more complete religion as compared the other two Ibrahimic religions(i.e Christianity and Judaism).As the preaching of Islam had most of its clauses related to that of the other two and that is the reason more and more people were convinced to follow up on the idea.
Along, with that there were exploration done by the Muslims across the regions, and they were able to assemble even an army for fighting battles with any oppressor inside these lands.So, along with this there were many influential people who accepted the religion and made it more easy to spread across the region.
As, the teaching of Islam influenced the art, culture and languages across the globe. So, generations after generation studied the Holy Book Quran, translations were made and the message was spread across billions of people across the generations.
And such an idea is termed to be as the historical continuity.
