khilij was a turk who were allies to mongols.
The khilij who destroyed Nalanda and killed Buddhist monks was an afghan mercenary. Not born in India.
These tribes also destroyed baghdad, the arabic centre of learning. The middle east have been under turk rule since 1258 until WWI.
The sack of baghad pretty much proved that islam inherited all those science and knowledge from others, and was unable to innovate. A truly innovative society is able to pick itself up from the ashes of war and rebuild. Just look at post WW2 Germany, Japan, South Korea and Singapore.