The Discovery of the Sarasvati River
The discovery of the Sarasvati River dealt a deathblow to AIT. It showed that the Sarasvati River, which supported the Harappan civilisation, was none other than the great river described in the Rigveda. This means that the Harappans were Vedic. Put another way, what it means is that cities and the other archaeological remains of the Harappan civilisation represents the material side of the culture and civilisation described in the Vedas.
That is to say, the people who created the Vedic literature also created the Harappan cities.
Ref: Sarasvati and the Vedic Civilisation by NS Rajaram