Short answers, pulled from the story.
Gopala founded the Pala Empire in 750 CE after being elected by the feudal chiefs of Gauda in Bengal. He was not of royal birth; an Arabic source described him as "not a king of noble origin". His election ended a period of anarchy that contemporary sources called matsya nyaya, or fish justice.
At its height under Dharmapala and Devapala in the early ninth century, the Pala Empire dominated the northern Indian subcontinent, stretching across the Gangetic plain to the Vindhya range. Dharmapala installed his nominee Chakrayudha on the throne of Kannauj and received tribute from rulers as far as Jalandhara. Devapala's inscriptions claim conquest of lands from the Himalayas to the Vindhyas and from the eastern to the western seas.
The Pala rulers were primarily patrons of Mahayana Buddhism, supporting Nalanda and Vikramashila universities and building major monasteries including the Somapura Mahavihara. At the same time, epigraphic evidence shows that rulers such as Mahipala I and Nayapala were initiated as Shaivites and sponsored temples to Shiva, Vishnu, and other Hindu deities alongside Buddhist institutions.
The Palas were known for the largest war elephant force among the major powers of the region; contemporary accounts noted that the Rashtrakutas had the best infantry and the Gurjara-Pratiharas had the finest cavalry, but the Palas had the greatest elephant corps. The Arab merchant Sulaiman wrote that the Pala king led 50,000 war elephants, though Ibn Khaldun set the figure at 5,000. Bengal lacked a native horse breed, so the Palas imported cavalry horses from the Kambojas.
The Pala Empire fell through a combination of internal rebellion and external pressure. The eleventh-century Varendra rebellion, led by the Kaivarta vassal Divya who killed Emperor Mahipala II, exposed the dynasty's heavy dependence on subordinate rulers. Historian Ryosuke Furui noted this rebellion decisively weakened Pala control over its samantas. The resurgent Sena dynasty ultimately replaced the Palas in Bengal, with Vijayasena defeating Madanapala to take southern and eastern Bengal.
The Somapura Mahavihara is a Buddhist monastery built by Dharmapala of the Pala dynasty, located in present-day Bangladesh. It is now a UNESCO World Heritage Site. The complex covers 21 acres and contains 177 cells, numerous stupas, temples, and other structures. Devapala later restored and enlarged it, adding sculptural themes from the Ramayana and the Mahabharata.