The 1950s IRA Border Campaign ended, they said because of lack of interest from ordinary people in Ulster who would have been (the Catholics) their natural source of support. BTW they deliberately did not target The RIC, who were the highly biggotted sectarian police force of Northern Ireland at the time during their abortive campaign and there was internment in the Irish Republic during it!
It is said that modern militant Irish Republicanism i.e. IRA, Official IRA, Provisional IRA, Irish National Liberation Army, Irish People's Liberation Organisation all have their genesis in the Civil rights movement being attacked by the powers that be in Northern Ireland and that there was no other realistic option accept to go down the militant route for ordinary downtrodden catholics. Also the Education Act 1948, providing free Second Level education for all, ultimately made the catholics forget what had been their place hitherto as Second class and sometimes Third class 'Citizens' there!
What If there was no IRA et al, would Northern Ireland be in as good a shape as it is now, especially for Catholics?
I strongly suspect that given the Afrikaner style abuse that 40% of the population had been subjected since the foundation of that statelette that the violent response was absolutely inevitable!