- Japanese invasions caused rice exports from Myanmar and Singapore to halt.
- A cyclone devastated crops, forcing farmers to consume their seed corn.
- The Japanese meanwhile were bombing coastal cities and using submarines to interdict shipping. Anticipating Japanese invasion, the British stockpiled food for the troops.
- They also exported food for troops elsewhere.
- This led to hoarding, shortages and price inflations which triggered famine.
- Britain, far from not caring, distributed 110 million free meals, but the scope of the economic chaos meant it wasn't enough.
The idea that Churchill actively (as in deliberately) caused the famine isn't supported by history. It's a modern invention by the same sorts of people who assert that only white Americans had slaves, and other historical re-interpretations designed to extract concessions from rich westerners.
The reality is far simpler and closer to what people would expect. Churchill didn't want there to be a famine in India, nobody did. The cause was the Axis attempt to take over the world and the fight-to-the-death that this led to.
Any attempt to attack Churchill or the British over what happened must, to be intellectually rigorous, reflect on the alternative. Churchill was indeed a racist but compared to Hitler, Churchill's views were nothing. If the Nazis had won the Battle of Britain not only would the British population have been enslaved in forced labor camps, thus ending any question of it aiding India, but the Empire would have come under direct Nazi control and D-Day would have been impossible.
With Hitler's full attention and resources on the eastern front it's possible that the Third Reich would have survived and become stable. If that had happened then, given Hitler's views and India's absolute economic weakness in comparison to what a unified Nazi Europe would have had access to, the full scale extermination of Indian and African populations could have followed. Only a major new front by the USA would have been able to stop it. This sort of hypothetical holocaust of Africa is a minor plot point in The Man In The High Castle.
So when people complain about the allocation of food in WW2, it seems like they're forgetting how badly things could have easily turned out in alternative timelines.