The flawed assumption beneath it was that if you could bribe them for long enough then eventually peace would become the norm and should there be any trouble the fat cat ringleaders would intervene. Except that they are now viewed as just another corrupt political class divvying the spoils between them. The same old resentments are still there and all it takes is a catalyst to reignite them. Most likely if one or other tribe is seen to be taking a larger slice of the pie.
All we really did was purchase a fragile ceasefire underpinned by the delusion that EU membership brings rainbows and kittens. If it can fall apart so readily just by Britain leaving the EU then it's fair to say that nothing was really settled. Further still, if we do see border checks in Ireland, that will more than likely be a failure of the process by way of having an impossibly complex outer EU border.
There is no reason in the world why a specific agreement cannot be made for customs and border cooperation in Northern Ireland. All it need be is a legal instrument calling on the many mechanisms that facilitate existing open borders. It's just a matter of political will. The only obstacle to it is the legal complexity created by the EU. We are about to see if the EU prizes conformity to procedure over peace.
To me though this highlights the bankruptcy of the entire EU narrative that the EU has brought peace. Rather than ending the internal stresses and strains it has merely buried them and let them fester under the surface. It's the same mentality as the then Yugoslavia and could just as easily, when the chips are down, tear itself apart just as rapidly.
The truth is that sectarian thuggery never really went away. The media just stopped publicising it. Should it resurface it will be more to do with a Northern Irish political class who have utterly failed to do anything useful with the powers given to them having instead used it as a platform for self-enrichment. To say that the EU was underpinning the peace is just to say that the EU was financing the bribes. You can't possibly tell me that we've had peace because Irish on either side of the border have bought into the larger European identity. If it's not true for the English then it is certainly not true for the Irish. It always was a house of cards and Brexit will show just how thin that narrative really is.
It seems to me that those invoking the spectre of further troubles do so out of entirely dishonest motives, placing their remain prejudices ahead of the common good. What else but grossly irresponsible can we call it?