India was much richer before. Muslims did not do the looting also properly. They were backward in that also. Educated British did in 250 years what Muslims could not do in over 600 years, that is plunder India systematically. British stole Indias wealth and took it to Britain and Muslims looted India and sent the wealth to Pak/Afghanistan. See the condition of those countries. Educated Britain is able to retain its wealth. Read history to see how Muslims brutally ruled India, especially wrote by the biographers of the sultans. Example, Tuzk-i-Timuri Hasan Nizamis Taj-ul-Ma'sir, Nizamuddin Awliyas Tarikh-i-Alai Kamiu-t Tawarikh, by Ibn-Asir Tarikh-us-Subuktigin Badaunis Muntakhab-ut-Tawarikh Sirat-i-Firuz Shahs Will Durants 'Story of Civilization'
If you cant get them in a library search the internet (a technology invented by Kaifirs). Good luck.