Famine is often the result not of an absence of food but of the inability of many people to buy what is available. That was so in Ireland's case: only one crop, the potato, failed; and during the famine, food was being exported from Ireland.
It has been said that there has never been a famine in a democracy. The famine in Ireland was not caused by "desperately bad luck", nor even by a fungus, but by a political system that kept a large majority of its inhabitants desperately poor. That political system was largely the creation of Englishmen.