The causes of the Indian Revolt of 1857 included a desire to preserve Indian culture and religion and a dissatisfaction with conditions for Indian soldiers within the Bengal army. Soldiers in that army, which was under British leadership, were mostly recruited from rural Indian families and had little ideological allegiance to the British Empire.
These soldiers (or "sepoys" as British officials called them) were underpaid, so there was little financial incentive to remain loyal to colonial interests either.
Adding to this dissatisfaction was the upheaval that British colonialism had already wreaked in the traditional Indian way of life. Not only were established hierarchies disrupted, but the people were taxed more rigorously than before.
Although the economic conditions of life under British rule were the driving cause of the Revolt of 1857, the attempts by colonial Christian missionaries to convert Indians were certainly an aggravating factor. Equally, certain practices within the military, such as the provisions to Bengal soldiers of flour cut with pulverized bones and rifle cartridges smeared with animal fat, were greatly insulting to the predominantly vegetarian Hindu sensibilities.
It was by appealing to the Indian people's fear of forced conversion and the loss of their religion that revolutionaries were able to unite Muslim and Hindu forces against their common British enemy.