Many people in the rest of the UK will be wondering how relations between the two key political parties in Northern Ireland have deteriorated so rapidly.
The more interesting question, perhaps, is this: how has power sharing at Stormont ever been possible, given the histories of the DUP and Sinn Fein?
Thirty years ago they were almost as antithetical as it is possible to imagine two parties to be – one the creation of the Rev Ian Paisley, and the other the political wing of the Provisional IRA.
Both parties have since become markedly more moderate. But I have an additional theory about the ability of the DUP and Sinn Fein to share power.
They are both, to some degree, Ulster nationalists – albeit one group wanting to be so under the umbrella of a united Ireland and the other wanting to live under the sovereignty of the United Kingdom.
To say this is not to play down the antipathy between them, that is apparent in a number of issues, including so-called legacy matters on the past (see below a link to my take on how the bail scandal shows we seem not even to be agreed that dissident terrorism is a serious offence).
Such tensions are at the heart of the current breakdown in relations.
But nowhere has a possible commonality between the two parties – a commonality that has enabled Stormont to survive for so long – been more apparent than in their attitude to public expenditure, which is spend, spend, spend.
There is real concern that the RHI scheme might have been kept open at the end for a bit longer to facilitate people getting on board. But the most benign explanation of the scandal is that the political leaders did not care much about the profligacy of RHI because they thought London was picking up the tab (it isn’t).
This is not the first time that all the main political parties in NI have been indifferent to the waste of taxpayer funds until it became apparent that there would be financial implications for Stormont.
The near collapse of the devolved institutions in 2015 was because Sinn Fein agreed to welfare reform, but then reneged on the deal.
In one constituency alone – West Belfast – 850 families were receiving more than the £26,000 welfare cap.
The DUP, however, never pushed for welfare reform (plenty of Protestant-loyalist working class areas do well out of welfare) until the UK government made clear that if Northern Ireland wanted a more generous welfare system, it would have to pay for it out of its own budget.
Few unionists argue for fiscal responsibility on its own merits. If you argue, as I have repeatedly done, that the Disability Living Allowance bill in Northern Ireland is disgraceful (almost 12% of the population are on it, and the annual cost to the Exchequer is £1 billion annually) you get little support.
Here is why: if that bill was halved, as I believe it could be, then £500 million would be taken out of the Northern Ireland economy per year.
I imagine that even Tea Party Republican congressmen, representing largely blue collar parts of America, pipe down their criticism of ‘big government’ when it comes to possible federal investment in their state.
But while our addiction to public money in Northern Ireland is understandable, as a deprived UK region, it does make me fear for the future of the Union.
It was of course a politician not of the right but of the left, JF Kennedy, who said: “Ask not what your country can do for you, ask what you can do for your country.”
That JFK approach seems to be buried much of the time now in Northern Ireland (although many Northern Irish people still serve bravely in the armed forces).
When he resigned this week, Martin McGuinness among other things criticised British governments for their austerity policies.
It was a staggering comment, given the generosity of UK governments towards Northern Ireland, stretching back decades, to counter the impact of IRA terror.
But it reminded me of a moment that I consider to be a nadir in the sort of Ulster nationalism, akin to Scottish nationalism, that is always seeking more money.
The deputy first minister was speaking to the press, just after the 2010 general election, and he warned that the British government was about to inflict “huge pain” in its fiscal programme.
Standing beside him was the then DUP leader and first minister Peter Robinson.
I was studying his body language, and while he did not nod in agreement with his republican deputy, there did not seem to be discomfort at that McGuinness comment.
How could there have been? Mr Robinson’s successful campaign in that election had led heavily on the “Tory cuts” supposedly advocated by the UUP-Conservative pact.
• Ben Lowry (@BenLowry2) is News Letter deputy editor