This is the biggest factor of all. Schools are the simplest way to cause (or prevent) language shift. A child that is literate in his native language is much less likely to lose it than one who can only speak and can't read/write in it.That would help but you would need industrial jobs in the Irish-speaking areas and less emigration from the Irish-speaking areas to save the language.
Also having national schools teach in Irish too would help after they were started in 1831.
OTOH Industrialism is a double edged sword : it could keep Irish speakers at home, but also invite non-speakers to move in.