As a result, when agriculture failed, there was no industrial production to buy food with.
So, you see, if the English had any fault in their government of Ireland, it was in that their rule was too soft and too unwilling to crush the backwards, regressive opposition.
> In 1800, the 1st Earl of Clare observed of landlords that "confiscation is their common title". According to the historian Cecil Woodham-Smith, landlords regarded the land as a source of income, from which as much as possible was to be extracted. With the peasantry "brooding over their discontent in sullen indignation" (in the words of the Earl of Clare), the landlords largely viewed the countryside as a hostile place in which to live. Some landlords visited their property only once or twice in a lifetime, if ever. The rents from Ireland were generally spent elsewhere; an estimated £6,000,000 was remitted out of Ireland in 1842.
> In 1843, the British Government recognized that the land management system in Ireland was the foundational cause of disaffection in the country. The Prime Minister established a Royal Commission, chaired by the Earl of Devon (Devon Commission), to enquire into the laws regarding the occupation of land. Irish politician Daniel O'Connell described this commission as "perfectly one-sided", being composed of landlords with no tenant representation.
Seems more like the wealth of Irish farmers was consistently extracted and sent out of the island, ensuring none of them can get out of poverty. Reminds you of something?
Accumulated capital, will by necessity flow towards other countries, where factories can be built and staffed. Meanwhile, because of the lack of potential competition with industry, the agricultural workers will be treated as poorly as the capital owner pleases. But that doesn't mean they'll be happy to be expelled from their lots of land, even if it'll help them.
None of that should be a mystery.
The Irish were successfully farming a number of highly nutritious crops. It's just that all of those were taken by the English, under the colonial system of the time.
The potatoes were one of the very few things they were allowed to grow for themselves (and are a great staple crop! near-complete nutrition all in one handy package!). That's why they were left starving when the potato blight hit, not because they were pathetic unenlightened regressives.