@MN5
I'll have a go on at this but it's a bit of a long story. Basically the team was elevated to Test status following quite reasonable performances in the 50-over World Cups in 2007, 2011 and 2015. That team was a bit of a relative golden generation for Irish cricket with the likes of Joyce, Morgan, the O'Briens, Rankin, Porterfield and Stirling all coming through at around the same time in what is a minority sport here.
However, as mentioned up thread, this is only Ireland's 12th test since their first one in 2018. There seems to be quite serious challenges regarding funding and this has impacted the fixture list quite a bit. For a few years there was a domestic three-day interprovincial championship but that hasn't been contested since 2019, raising the question of how can Ireland expect to produce test players with no domestic first class cricket? A lot of the 2007 to 2015 era team were able to develop this experience in English county cricket but that option is mainly off the table at the moment as Irish players are now considered to be 'overseas' and so less attractive to English counties. Another little flurry of players did emerge just after the Covid years in Little, the Tectors and Tucker - possibly the last ones to benefit from having had a domestic multi-day competition to play in. In more recent years many of the debutants and development squad members have been Irish-qualified players originally from overseas.
In response to the question posed elsewhere concerning why this is a four-day game? Again, I wouldn't be surprised if it's as simple as that it's because they are less expensive to host than five-day games.