My view is that if Ireland hadn't done their tax shenanigans then none of these companies would be here and it would be an absolute backwater (software dev-wise). Ireland has some really great education and talent but the culture, infrastructure, and personal taxes don't lend themselves to a bootstrap/startup friendly environment imo. So even today a ton of Irish people move to the UK, Canada, or Australia for better jobs.
The specific engineering positions[¹] seem to have a significant rate of customer support/sales/market; it seems that Ireland isn't a technical research center. I haven't looked at how the mix of open positions is in SV/USA, though.
¹=https://careers.google.com/jobs/results/?category=DATA_CENTE...
They're here because of tax, yes, and Ireland is in no meaningful way a leading startup centre. But Dublin in particular has more people working in software than (say) London.
I have seen estimates which suggest the total tech industry employment in Ireland, not Dublin the whole country, is something like 100k. London had this many open vacancies in tech per week earlier this year. And that is assuming all these jobs are equal which, of course, they are not (you are unlikely to open a support centre in London).
London's VC market alone is multiples of the next largest city in Europe (which I believe is Paris). I think Manchester is actually a larger VC market than Dublin (and Edinburgh is probably coming close).
According to this, 9% of the population in Dublin are software developers. By comparison, London seems to be at 7.7% according to the same metric.