What made the Indian rebellion against the British and how they all decided that the British is the only enemy to them?

The sepoys felt that the British did not respect their religion and this was a major reason for their mutiny in 1857 that prompted the Great Rebellion.

late March 1857 a sepoy named Mangal Pandey attacked British officers at the military garrison in Barrackpore. He was arrested and then executed by the British in early April. Later in April sepoy troopers at Meerut refused the Enfield cartridges, and, as punishment, they were given long prison terms, fettered, and put in jail. This punishment incensed their comrades, who rose on May 10, shot their British officers, and marched to Delhi, where there were no European troops. There the local sepoy garrison joined the Meerut men, and by nightfall the aged pensionary Mughal emperor Bahādur Shah II had been nominally restored to power by a tumultuous soldiery. The seizure of Delhi provided a focus and set the pattern for the whole mutiny, which then spread throughout northern India. With the exception of the Mughal emperor and his sons and Nana Sahib, the adopted son of the deposed Maratha peshwa, none of the important Indian princes joined the mutineers.

it is due to the halo effect as the impression of the boy created earlier.on the mind of the principle affected his decision