4 ideas
Sita Ram joined the Company's army as a young Brahmin, drawn by his uncle's stories of pay and glory. During the First Afghan War he was captured, sold into slavery in Afghanistan, and escaped years later. When he returned home, his village and family treated him as ritually polluted by his time among foreigners and captors, so the service that was meant to raise his standing cost him his caste standing instead.
The narrator argues that the Bengal Army decayed from the inside long before 1857. Older British officers had spoken the sepoys' language, known their families, and shared their hunting and hardships. Younger officers held them in contempt and deferred to distant rules. Once that personal bond was gone, rumours such as the greased cartridges could turn ordinary grievances into open revolt, because no trusted officer remained to contradict them.
In the Bengal Army, Indian soldiers were promoted strictly by length of service, not ability. Sita Ram reached subedar, the highest rank open to him, only after about fifty years, when he was old and spent. Under this system every Indian officer arrived at command too late to use it, and even the most senior of them ranked below the most junior British officer.
What the text says about loyalty, grievance, and British virtue has to be read against what the translator had reason to keep, soften, or add. The rarity that makes the source precious is also the reason it can't be fully verified.