We must carefully differentiate crop failures from starvation. Crop failure is a neccesary but not sufficient cause of starvation. Crop failures occur all the time, but people don’t always starve.
In moderately wealthy countries with a modern transportation system farmers whose crops have failed aren’t depending on those crops for food, they grow crops commerically not for subsistence. In modern countries crop failures may be a business disaster for the farmer, but they aren’t in any more danger of starvation than any other businessman whose business goes bankrupt. Even if the whole region experiences crop failure food from previous years will still be plentiful, food from around the world can be purchased, the country is not dependent on domestic production to feed itself.
Then there are three other cases. First, modern countries with totalitarian governments. In this case, a crop failure may mean starvation if the political authorities deem it too dangerous to import food, or to let anyone know that a crop failure is occuring. Food could be purchased on the world market, but it would be a PR disaster for the regime to let that happen. Typically cities are still supplied with food, but people in the countryside are left to fend for themselves. This is a pretty simple case where starvation is directly caused by politics.
Then there is the case of a third world country dependent on subsistence farming. A crop failure can mean starvation, but there is plenty of food aid lying around to keep people from dying. Even though people and governments in the area are too poor to buy the food they need, there is a humanitarian infrastructure in place to get food to pretty much everyone who needs it, barring extremely isolated places with very few people anyway. Sure, tribal leaders and warlords will use the food aid for their own purposes, sure some will get skimmed off and resold, but the answer is just to pump more food in and accept the corruption as the price of doing business.
But if the crop failures take place during a war then it can be very difficult to get food to people, because there are people with guns who will shoot, kill, and loot the humanitarian and refugee workers. If the relief workers are likely to be killed they can’t distribute the food. And the warlords and bandits might distribute food to their own followers, but they will certainly actively try to disrupt food distribution to enemy ethnic groups or factions.
And of course, war itself is a major cause of crop failures, because subsistence farmers abandon their fields and become refugees, or are killed, or their food stores are stolen. So food production plummets. This is what caused the famines in Ethiopia. It wasn’t so much that the weather was particularly bad, it was that all those starving refugees couldn’t go back to their lands and grow food, because if they did they’d be killed.