The reasons for decline of Mughal empire are as follows:
Aurangzeb religious policies were not in sync with the policies of his predecessor. His intolerant attitude led to the decline of the social fabric in Delhi Durbar. Other stakeholders were not happy with his religious policies.
His strategy to conquer deccan and transcending boundary further south proved to be harmful for the solidarity of the empire. His stubbornness to accept the regional independence also led to his downfall.
He was not apt in forging alliance.
Later Mughals were not capable enough.
Mansabdari system, Jagirdari system were now became hereditary and hence were not economical. This led to pressure on treasury.
In the absence of a fixed rule for succession, the empire was always plagued after the death of a King by a civil war between the princes resulting in loss of life and property and of capable military commanders.