Question

what are the major causes for the down fall of the mughal empire

Answer 1

Weak Successors
Weak Milatry Administration
Rivarly among nobles
and more

Answer 2

Aurangzeb highly overturned the secular and liberal policies followed by earlier Mughals. This combined with his long campaign in the Deccan took a toll on Mughal dynasty.
Also, he was followed by a string of weak rulers due to which Mughal power swiftly declined.