There is a stronger argument to be made that it was because of the establishment of Buddhism as the de-facto state philosophy/religion/practice in North/Northwest part of India that the Islamic invaders could conquer India. Buddhism for all its intellectual/ethical/moral strengths was not a pragmatic religion. It ignored the realities of Life in favour of higher ideals in a context ill-suited to its survival and hence paid the price at the hands of barbaric muslim invaders. This happened through the elevation of Ahimsa into an all-encompassing tenet of state policy which severely sapped the Martial Spirit of the population and thus could offer no resistance to invaders bent on genocide. Prior to Buddhism (and Jainism) while Ahimsa was considered one of the central pillars of Hinduism its limitations in the practical world were acknowledged and Kings were expected to protect by force if necessary, those practicing Ahimsa as a way of life. With this gone, North/Northwest India was easy prey to barbaric muslim invaders who did not play by the same rules.
During their conquest of Sindh, the Arabs brought the non-Muslims into the category of ahl al-kitab, considering them ahl al-dhimmah (protected subjects) and thus practicing a certain amount of non-interference in their religious lives under the condition that they fulfil a number of obligations that came with this status. Since both Buddhism and Hinduism are literate religions with scriptures, the precedent of assimilating Zoroastrians into the category of ahl al-kitab was extended to them as well. The dhimmis were obligated to pay the jizya for following their ancestral religion. The historian Al-Baladhuri notes a decision by Muhammad bin Qasim in relation to a Buddhist vihara and Aror that after conquering the city through a treaty (sulh) he agreed not to kill the people and enter their temple, in addition to imposing kharaj on them.[29] The Buddhists had petitioned the Arabs for the right to restore one of their temples and it was granted by Al-Hajjaj ibn Yusuf. However, this decision was later violated by the Pact of Umar and subsequent Muslim law codes which prohibited the restoration of existing non-Muslim religious structures as well as the building of new ones. Despite this fact, Buddhist inscriptions were still being recorded in the eleventh century.[28] Some Buddhists also fled and emigrated from Muslim-ruled areas into other regions. Unlike Brahmanical worship, Buddhism rapidly declined in Sindh after the eighth century and it virtually disappeared by the eleventh century.
