Ireland seems to be making a reasonable fist of having English and Irish; most business is conducted in English […]

Historically, that’s mostly because of colonial rule by the English government.

For decades (if not centuries) the Irish language was severely suppressed and might have even died out, if not for the continued efforts by the Irish people to preserve their language and cultural identity.

A combination of the introduction of state funded […] primary education, from 1831, in which Irish was omitted from the curriculum till 1878, and only then added as a curiosity, to be learnt after English, Latin, Greek and French […]. The National Schools run by the Roman Catholic Church discouraged its use until about 1890.

It’s only quite recently that Irish has become an official language in Ireland:

In July 2003, the Official Languages Act was signed, declaring Irish an official language, requiring public service providers to make services available in the language […]

Of course, the fact that Ireland is trading a lot with the UK and other countries in the anglosphere and EU, is a reason to keep English as a major language.