Also it is (and was) the only English speaking country in the eurozone.
Tax was a huge factor in drawing some of the big names but the double-Irish (the worst aspect of tax avoidance) had been phased out. Corporate tax is 12.5% which is lower than the majority of EU countries [1] but the existing ecosystem of companies has also helped create an attractive labour pool. If it's purely tax everyone would move to Hungary (9%).
A number of European countries have near 100% English literacy and allow for document workflow and accounting in English. I suspect it's mostly the taxes.
I totally agree that English can be used entirely for businesses in other euro countries but for a US company it is attractive for employees/families to be in country where English is an official language.
Tax was a huge factor in drawing some of the big names but the double-Irish (the worst aspect of tax avoidance) had been phased out. Corporate tax is 12.5% which is lower than the majority of EU countries [1] but the existing ecosystem of companies has also helped create an attractive labour pool. If it's purely tax everyone would move to Hungary (9%).
1: https://taxfoundation.org/2021-corporate-tax-rates-in-europe...