Obviously Czechoslovakia has a great excuse, not having existed for 32 years, but neither Czechia nor Slovakia come close to Ireland, either is terms of Euro-value or number of software jobs.
Ireland's software exports dwarf Poland, Czechia, Slovakia, and the Baltics combined. That's ignoring the inflated GDP figures from international IP revenue tax-dodging.
The days of the Double Irish are long gone and comparing effective tax rates paints a very different story, so this is 5 years out of date in as true as it ever was.
Even excluding the EU IP revenue of multinationals with EMEA HQs in Ireland, real software development revenue is over double Poland, Czechia, Slovakia, and the Baltics combined.
But that's irrelevant, as ghost HQs can avail of Ireland's tax regime with minimal employees.
Ireland's extremely educated workforce and exceptionally stable and peaceful governance along with business friendly economic climate are the reason Ireland is a software powerhouse, independent of tax regime (which is not particularly conducive to large employers).
Also there are quite a few successful gaming companies in central and eastern Europe - like CD project (Witcher/Cyberpunk) in Poland and Factorio, Mafia, Kingdom Come from Czech Republic.
Also on the IT driven services are there are quite big companies like like Alza/Allegro (eq. local Amazon), Seznam (eq. local Google), Windy (weather), etc.