One current theory is that trade with Mesopotamia (which was very important to the Indus Valley civilization) slowed or stopped, due to Mesopotamia's own troubles at the time.
The newest accepted theory for their demise by schollar explains that climate change is the most probable reason . Many studies were made to confirm that and it became official.
it was the continuation of the roman empire in its eastern provinces during late Antiquity and the middle ages..it was known for the longest lasting medieval power.
