Explain what happened to the Amaravati Stupa and why?

Amaravati stupa was discovered accidentally. In 1796, a local raja who wanted to build a temple stumbled upon the ruins of the stupa at Amaravati. He decided to use the stone, and thought there might be some treasure buried in what seemed to be a hill. later in 1854, Walter Elliot, the commissioner of Guntur (Andhra Pradesh), visited Amaravati and collected several sculpture panels and took them away to Madras. He also discovered the remains of the western gateway and came to the conclusion that the structure at Amaravati was one of the largest and most magnificent Buddhist stupas ever built. By the 1850s, some of the slabs from Amaravati had begun to be taken to different places: to the Asiatic Society of Bengal at Calcutta, to the India Office in Madras and some even to London. 
HH Cole tried his best to save it but he could not save Amaravati but his word was able to save Sanchi. It is because when Amaravati was discovered the value of it was not known and how important it was to keep the thing where it was. Hence for now as Amaravati stupa all we ahve is a mound.