Namaskaram Swami,,

Bhagavadgita was preached by Lord Srikrishna almost at the end of  Dwapara yuga ( almost 5200years back). However as per various articles & books, Gita was known to the world during 3rd or 4th BC( almost 2400years back).  What happened the remaining 3000years….?  The mankind were not aware of this holy message of Srikrishna…?

Please clarify my doubt…

regards,

Subramaniam