Why was the Gyanvapi Mosque never destroyed by Marathas even though it was built by Aurangzeb after destroying the true Kashi Vishwanathan temple?

 The Reason and Background for same are:

Marathas started becoming Militarily Strong after Decade of Death of Aurangzeb (1720) especially after ascension of Baji Rao 1 ( 1720–1740).

They always entertained the idea of demolishing Gyan Vapi Mosque and reinstating Kashi Vishwanath Temple. They started reaching North India by 1740s. Balaji Baji Rao (1740 - 1761) especially instructed in a letter in 1751 (still preserved) to his Brother Raghunath Rao to reinstate Kashi Vishwanath Temple. Raghunath Rao’s Lieutenant Malhar Rao Holkar publically stated in 1755 his idea of demolishing Gyan Vapi Mosque.

The reason they cannot do so is because they cannot conquer and Annex Awadh Province. Especially because of 4th & 5th invasions of Ahmed Shah Abdali (1757 & 1761). 5th invasion of Abdali which culminated in 3rd Battle of Panipat seriously weakened Maratha Power in North India for about a decade.

During this decade British East India Company made gains and ultimately defeated Nawab of Awadh in 1765. With subsequent treaties and especially 2nd Treaty of Allahabad (1775), Benaras came under British control. Warren Hastings explicitly denied any permission for demolishing Gyanvapi Mosque. But British finally gave permission to Ahilya Bai Holkar ( Daughter in law of Malhar Rao Holkar) in 1780 to create Kashi Vishwanath Temple adjacent to Gyan Vapi Mosque.