Aurangzeb was cruel because he wanted to be the head or the supreme. he wanted welfare of people in indirect way. since, it was other thing that the main factor of downfall of mughal empire was aurangzeb.
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Now this is something very controversial . when the succession wars ensued between shahjahan's son's, aurangazeb was backed by the ulema or orthodox wing of the muslim aristrocrats of the mughal court. so when he came to power it is obvious he had to work for their satisfaction. but he was not cruel 
at least history says so......