luxembourg(4th), switzerland (6th) denmark(11th), netherlands(16th), austria(17th) they are all higher in rankings (in that order)
Followed closely by Belgium ((22) and france(24) and then czechia (40) and lastly poland (58)
So they are right in the middle, 4 of the countries that they share a border with have higher gdp per capita, and 4 have lower.
So the argument that it is GDP per capita, and PPP, though not incorrect, is invalid, because it would have had to have shown more than double its real GDP to be above south korea.
People are more widespread in ireland than the UK. The Uk density /km² is about 270 for the UK and only 70 for ireland. (65 million people versus 5 million approxomately)