Taxila and Nalanda universities housed all of the original works and manuscripts on buddhism in India. For hundreds of years people all over India would send in any relevant material so it could be kept safe and available to all scholars.
The Muslims, upon finding that no koran was kept in these places, set fire to all the works. Apparently so many manuscripts were kept at Nalanda that it is said to have burned for days. They generally burnt any material which they considered heretic. Lots of Jain, Vedic and Tantric material was lost in the same way.
Its a shame that the only surviving Buddhist material comes from outside of India from Nepal, Tibet, south east asia, China and Sri lanka as these works are copies, not original works.