Here is my idea.
During the famine grain was being hoarded my several estates, shipfulls of grain were being exported from Ireland. This exacerbated the famine.
But look at it this way - there was a bad harvest, which by itself would have caused an increase in grain prices. But it precipitated and attack on commodity prices by a coordinated group of investors. They bought grain and withheld it from the market, pumping prices. Then they sold small amounts at inflated prices.
The actions of Westminster, where they decided year after year not to intervene, is said to be because they didn't want to provoke shocks in food prices in England. If you take them at their word, it was a genocide - they worsened (or created) a famine (and consciously killed millions) for local political reasons.
But looked at the new way, they were facilitating an investment scheme by important wealthy businesses. By withholding food from Ireland (food which was mostly produced in Ireland) they were allowing the scheme to run for longer. This is typical in modern England, that the bankers' interest is the highest priority for government. Understanding that is key to understanding why the UK behaves as it does. And the famine lasted several years, only because of Westminster's actions.
Makes sense?