As you will have gathered from previous posts and the Wikipedia links, Ireland's Jewish population had a cultural significance out of all proportion to its size. Sizewise, Ireland North and South had a Jewish population of analogous size to those of Denmark, Sweden, Norway, Finland or Bulgaria. And like them, the largely self-employed and urban Jewish populations weren't resented as they weren't rivals for land or jobs.
To increase the size, or even arrest the decline, of Northern Ireland's Jewish population (I know very little about the Dublin or Cork congregations) you would need to butterfly away both the Bolsheviks victory in the Russian Civil War and the Holocaust. Eastern European Jews seeking a better life and relative freedom from persecution, constantly replenished any losses due to assimilation or migration to larger Jewish centres up until the foundation of the USSR (allowing migrants to seek a better life and freedom from persecution was an affront to its ideological raison d'etre) and the virtual elimination of Eastern European Jewish communities by the Holocaust.
The NI government under Lord Craigavon actively encouraged Jewish businessmen and engineers expelled from Germany and Austria to bring their skills to NI during the late 1930s (one of the few things that Stormont did that we can point to with some pride). Trouble was we were (and are) a small economy.
Post WW2 new Jewish immigration virtually ceased, most of the Jewish refugee population moved on to the USA or Israel. I personally knew the only two to remain in NI, Mrs Yannie Kitzler and her son Larry (who worked with me in the Civil Service up until his retirement in 2002). Mrs Kitzler remained semi-observant, but Larry converted to Christianity and was buried a Methodist in 2014.
Which illustrates why the small Jewish population has entered into a cycle of decline, the mainland UK,the USA and Israel offer much better social prospects to the religiously observant including chances of same faith partners, all have much larger economies and the small remnant population is increasingly being assimilated by interfaith marriages and even religious conversions. Much like (Southern) Irish Protestants, Catholics in some parts of England and the (White Russian) Orthodox communities in the UK and France prior to 1989.