“They didn’t understand the repercussions of being Brexiteers.”
I can understand their concern, since they must realise, even though they don't like to think about it, that everyone but them wants a united Ireland, whether on principle or simply to be rid of NI, and sooner rather than later, so for different reasons it suits both Dublin and London for this situation to carry on, since it must make union with the South an increasingly attractive proposition.
Since the Unionists are paranoid anyway, and know their days are numbered because of simple demographics (and because the DUP is despised by everyone else, British and Irish alike) they must be feeling pretty nervous, which I really hope doesn't go any further than the Unionist paramilitaries making vaguely threatening noises to remind people they're still around.
I've been reading Sasha Swire's marvelously indiscreet and bitchy memoir of being a Tory politician's wife, and I rather liked her description of what it was like when her husband, Hugo, was David Cameron's Secretary of State for Northern Ireland, and responsible for the Peace Process -- like having to carry around a large and valuable Ming vase all the time.
I just pray no one drops it.