There is a deliberate attempt by modern Historians (who take the word of muslim historians of medieval ages as gospel) to portray:
a) India was a sitting duck which was easily conquered by Muslims.
b) Muslims were very cultured!
Both these assertions are absolutely false. I will tackle the first one now and the second one later.
Please read
Hindus saved Hinduism by fighting against Muslim invaders Regards,
-Digvijay