The famine was caused by monsoon failure. This was not a new phenomenon, it was known among locals that monsoons could fail bringing about a prolonged dry season. The precautions set in place by locals were large stores of grain to rely on if the rains never came.

You could attribute the demand imposed on grain by The East India Company for the elimination of these grain stores. There were fewer reserves of food because there was a market extracting grain out of the country.

Another factor you can give the EIC credit for was the way work camps were organized. To prevent overcrowding of people looking for work and to ensure workers who actually had stamina to perform, a policy was put in place putting a minimum distance of residence from work site. People could not go to a job site that was in their village. They would have to walk several miles to technically be eligible for employment.

These workers were malnourished, their pay being about a pound of rice per day. This is hardly enough for one person to have adequate nutrition with, and that rice was divided among more than one person at home.

Combining the long trek for work, improper nutrition, and pilfered backup reserves among other factors resulted in these staggering death tolls.

This is what I gathered from the dark and informative book recommended to me by my 18th century european history professor, Late Victorian Holocausts by Mike Davis.

I hope someone can give more detail than I did.

If I could pose a follow-up: what about 1943?