I think your question could best be answered in two parts. I’ll focus first on describing how Ireland managed to weather the storm of British imperialism so well. Second, I’ll talk a bit about how a post-independence Ireland went from being an underdeveloped state by European standards to the successful state it is today. But first, a bit of a disclaimer.

Ireland’s relationship to imperialism is complex. On one hand, Ireland and its people were the victims of British imperialism and oppression, and many of its people (especially the poor, Catholic population) suffered greatly under British rule. On the other hand, Ireland did play a role in expanding the British Empire overseas, and over the last thirty years or so Irish historians have become increasingly interested in exploring this overlooked bit of Irish imperial history, even going so far as to say that Ireland’s cooperation with Britain in matters of empire resulted in Ireland enjoying a more privileged relationship with Britain in the empire more akin to Canada or New Zealand as opposed to a subject of exploitative British imperialism like India.

In the interest of full disclosure, this is a controversial topic in Irish historiography, first and foremost because the Irish suffering under British rule was so great (especially in regards to the famine) that any allegations that Ireland could have benefited from imperial rule could be seen as distasteful at best and biased, agenda-driven ahistorical hogwash at worst. Although this argument has become less taboo since it first cropped up in literature during the early 1990s, it’s still worth noting that the historians who are writing about this are not trying to erase or mitigate Irish suffering at the hands of the British, but rather they are trying to paint a fuller picture of the relationship, arguing that Ireland can be both a victim of and complicit in the British imperial system. The latter points, I think, could help answer your question.

Part I: Ireland and Empire With that out of the way, let’s look at what role the Irish played in the British Empire, and what set Ireland apart from other British dominions. First, it’s important to note that as England and Ireland share a long (and very troubled) history stretching back to the 12th century — that’s four hundred years before England would attempt to establish their first overseas colony at Roanoke. This history would lead to a much deeper relationship than England would later have with their future colonies. As England slowly eased and/or bludgeoned its way into the other realms of the isles, the constituent parts therein would retain a position of privilege compared to the future dominions of England. Even so, I would say the system was less “England being the first among equals,” and more “Ireland was the second among inferriors,” behind Scotland, and ahead of nearly everyone else.

Irish historian Hiram Morgan covers the evolution of the relationship between Ireland and empire in his article, “An Unwelcome Heritage: Ireland’s Role in British Empire-Building”, but I’ll summarize a short version here. From the late 18th century onwards, discrimination against the Irish slowly decreased and their influence over and participation in the British Empire slowly increased. While Ireland lost its parliament under the Acts of Union ca. 1800, they were allowed to elect and send representatives to Parliament in Westminster because the Acts of Union did just that; they unified the Kingdom of Great Britain (itself made up of England and Scotland) and the Kingdom of Ireland into a single state, subject to a single monarch and legislature. This status of political union sets Ireland apart from future colonies politically, as future overseas colonies would never enjoy the same level of political union. After the repeal of the anti-catholic laws in 1830, representatives to Westminster included catholics as well as protestants. Irish MPs worked with others in governing and expanding the empire, while the Irish soldiers continued to expand their role in the British military. For example, of the 22 Victoria crosses awarded to soldiers after the Indian mutiny, 13 were awarded to Irishmen. Catholic Irish soldiers served all over the empire, while Protestant Irish aristocrats filled the officer corps. Millions of Irish also emigrated across the empire during the 19th century, where they imparted their own brand of imperialism on native peoples they encountered as they tried to escape from under the thumb of British rule. Morgan doesn’t name names, but notes that some have argued that, “Catholic Ireland created its own spiritual empire” in the colonies they emigrated to. Obviously the big caveat here is that the Irish were pushed from Ireland (in cases of transportation and famine-time emigration, brutally so) far more frequently than they were pulled by the desire to spread their way of life abroad.

Still, Irish emigrants made up significant parts of the population in British colonies, and by extension, often ended up in charge of said colonies, while at the same time domineering over native populations in true imperialist fashion. As Ireland became more and more ingrained in empire building via the military, colonization, administration, and policy-shaping, they began enjoying a status more akin to imperial associates rather than imperial subjects. Again, this is not to say they suddenly became equals in the UK — far from it. Ireland was not immune to the negative effects of imperialism, and again, see the famine as a prime example. However, as Ireland moved into the 20th century, the gap between the social and political status of the Irish and the English was shrinking. Morgan is careful to mention that Ireland received little in direct economic benefit from their role in the empire, save the influx of cash from emigrants who sent money home to their families, helping those that stayed behind to stay afloat through the famine and the rough decades that followed.

Just how much that gap had shrunk depended on who you asked. Unionists argued that Ireland was an essential part of the Union, and its heavy industry in the north and agricultural output were key to British prosperity. Home Rulers, who sought greater autonomy for Ireland in the Empire, argued that Ireland was distinct enough, and its needs unique enough, that it deserved to be governed by an Irish parliament. Separatists argued that Ireland was little more than a colony being ruled by an indifferent parliament from abroad. Regardless of the prevailing opinion at the time, economically, Ireland was in a comfortable position on the eve of the First World War, much like Britain, although Britain’s economy was far more industrial, and Ireland’s more agrarian. While not “backwards,” Ireland’s economy was not at the forefront of industrialization, but still of similar scope to small, more agrarian European states like Portugal, the Scandinavian countries, or Italy.