Ireland was colonized by the vikings from the 8th century onward, who continued their long history of seaborne trade even after they abandoned the practice of raiding for which they are more famous. So they had the liquid wealth (primarily gold and silver) and the cultural willingness to acquire slaves. The viking settlements became the first large towns in Ireland, and supported the first sophisticated cash economy on the island capable of generating the liquidity for purchasing slaves from abroad. While the native Celtic Irish also had a history of slave-holding and raiding (see, e.g., the life of St. Patrick), they produced and held significantly less liquid wealth than the viking settlers and never established the large scale trading communities necessary for slave markets to emerge. As a result, pre-viking native Irish slavery did not involve large scale cash-based slave trading.
Also worth mentioning that the scale of the medieval British slave trade was likely small relative to the total populations of either England or Ireland, because it disproportionately consisted of the sale of young women as concubines. Note that there is a difference between the size of the enslaved population and the size of the slave trade. While as much as 30% of the population of Anglo-Saxon England may have been enslaved and the vast majority of those were economic slaves, only a small portion were ever bought or sold on the slave markets, and an even smaller portion sold to the foreign market.
There was simply less demand for purchasing economic slaves because Ireland did not have a robust cash economy for agricultural goods that would have generated the revenue necessary to acquire slaves. That is, acquiring economic slaves for cash only makes sense if those slaves can be used to generate further cash. Concubinage was an exception because in economic terms it is a form of consumption rather than investment. Economic slaves were more likely to be acquired via raiding or conquest, which effectively converts a surplus in defense spending into an economic investment.
Which isn't to say economic slaves weren't bought and sold, just that demand for them was weak and likely the trade only existed because acquiring them was a "free" byproduct for a seller who acquired them while conducting raids aimed at acquiring liquid wealth and potential concubines. As in, a viking group may have raided a village with the specific intent of seizing any valuables and young women, but figured that they might as well take the young men too because they could at least get something in exchange for them. Demand for agricultural economic slaves was low because the productivity of early medieval agricultural workers was extremely low. Once the Christian church turned against concubinage and extra-marital relationships in general, the demand for slaves disappeared, reducing the incentive to raid and thus the incidental production of economic slaves. Which is a corollary of the argument the OP article proposes for the decline in Norman slavery.
Bottom line, a relatively narrow class of wealthy traders and viking raiders in Ireland would have been purchasers in the slave markets, even though the country as a whole wasn't especially wealthy and did not need to be for the slave trade to exist.
Also worth mentioning that the scale of the medieval British slave trade was likely small relative to the total populations of either England or Ireland, because it disproportionately consisted of the sale of young women as concubines. Note that there is a difference between the size of the enslaved population and the size of the slave trade. While as much as 30% of the population of Anglo-Saxon England may have been enslaved and the vast majority of those were economic slaves, only a small portion were ever bought or sold on the slave markets, and an even smaller portion sold to the foreign market.
There was simply less demand for purchasing economic slaves because Ireland did not have a robust cash economy for agricultural goods that would have generated the revenue necessary to acquire slaves. That is, acquiring economic slaves for cash only makes sense if those slaves can be used to generate further cash. Concubinage was an exception because in economic terms it is a form of consumption rather than investment. Economic slaves were more likely to be acquired via raiding or conquest, which effectively converts a surplus in defense spending into an economic investment.
Which isn't to say economic slaves weren't bought and sold, just that demand for them was weak and likely the trade only existed because acquiring them was a "free" byproduct for a seller who acquired them while conducting raids aimed at acquiring liquid wealth and potential concubines. As in, a viking group may have raided a village with the specific intent of seizing any valuables and young women, but figured that they might as well take the young men too because they could at least get something in exchange for them. Demand for agricultural economic slaves was low because the productivity of early medieval agricultural workers was extremely low. Once the Christian church turned against concubinage and extra-marital relationships in general, the demand for slaves disappeared, reducing the incentive to raid and thus the incidental production of economic slaves. Which is a corollary of the argument the OP article proposes for the decline in Norman slavery.
Bottom line, a relatively narrow class of wealthy traders and viking raiders in Ireland would have been purchasers in the slave markets, even though the country as a whole wasn't especially wealthy and did not need to be for the slave trade to exist.