Islam has deliberately "lost" the Hindu history of Arabia 2,500 years before Mohammed to the advent of Mohammed.
What are they suppressing? Hindu conquest and occupation of the area. Mohammed's Hindu family line as keepers of the Kaaba. The Kaaba's origins as a Hindu temple. The origins of Al Lah. The tradition of going around the Kaaba seven times, pointing at the black rock when saying "Al Lah Akhbar." The origin of the Zam Zam holy water well near the Kaaba. The origin of the black rock sticking out of the corner of the Kaaba, surrounded by a metal facsimile of a vagina. The origin of the moon motif representing Islam. The origin of the name, "Arabia."
Here's some more. (Turn the sound off)
Google the library of Makhtab-e Sultania whose collections include documents from the "forgotten" period.
Here's the inside of the Kaaba. Note the graven images of the sun & moon, in violation of the Koran. Also, there is a man worshipping before a plaque that is not in Arabic.
edited: August 04, 2017 orderofsaintpatrick.org/hindu/hindu-islam.htm