How did the Maurya Empire gain maintain and lose power?

In 322 BC Chandragupta Maurya managed to overthrow the Nanda Dynasty in northern India, beginning expansion of the kingdom westwards across central and western India. Maurya Empire was also largely expanded during the reign of emperor Ashoka, who was one of the greatest emperors in Ancient India. After Ashoka's death the Empire began to decline and eventually it was disestablished in 185 BC, when the last emperor of Maurya Empire, Brihadratha, was assassinated during a military parade by the Brahmin general Pushyamitra Shunga.