The trouble was an eruption of simmering political tensions among loyalists - who support Northern Ireland staying in the UK - that pre-date the 2016 Brexit referendum, but which have escalated since that vote.
A three year stand-off between London and Brussels over how to police the frontier was in 2019 resolved in a way that was devastating to unionists, creating a barrier between Northern Ireland and the rest of the UK - which is anathema to unionists.
The so-called Northern Ireland Protocol, which established that trade frontier in the Irish Sea, was agreed by Boris Johnson 18 months ago but it took until this year for its impact to become visible.
Irish republicans and the Republic of Ireland government successfully lobbied against any increase in checks at the Irish land border, not even so much as CCTV.
That this demand was granted by a government in London that prides itself on being Conservative and Unionist fuelled the sense among unionists that Irish republicans - Sinn Fein - will always get their core demands.
Loyalists say that Sinn Fein does not want Northern Ireland to work, and was allowed to collapse the local parliament at Stormont in 2017 over what unionists believe was a pretext over a financial scandal relating to an energy scheme known as 'cash for ash'.
The impasse came to an end last year, but involved the granting of a key Sinn Fein goal of an Irish language act - which unionists believe will become a cultural wedge between the two main communities in Northern Ireland.
The sense of political alienation in many of the loyalist areas was fuelled by a major funeral held last summer for a former IRA leader in west Belfast, attended by dozens of senior politicians in Sinn Fein.
Last week a lengthy investigation into that gathering, estimated at thousands of people, ended without any of the participants getting even a police caution for what was seen across Northern Ireland as a flagrant breach of social distancing rules.
This solidified the unionist perception that Irish republicans always get special treatment from the authorities.
But the riots are also a reflection of social difficulties in deprived areas where many of the inhabitants are NEETs - not in employment, education or training.
Such problems have been exacerbated by lockdown. Many of the rioters have been teenagers, who in other parts of Belfast have also been implicated in non-violent breaches of social distancing such as holding large house parties.
Politics in Northern Ireland has been fragile for decades. Since the 1998 Good Friday Agreement the region has been governed by a system of local power sharing at Stormont, in which political irreconcilables form what is known as a mandatory coalition.
Since 2007, the two main parties have been the unionist DUP and the republican Sinn Fein, who have fundamentally different ultimate objectives: in the former case to stay entirely in the UK, in the latter to join with the Irish Republic to form a single island jurisdiction, outside the UK.
This means that there are sporadic disagreements and tensions at Stormont, which at times in the last 23 years has led to the suspension of devolved government, and direct rule from London.
Think of it like Nigel Farage and Jeremy Corbyn having to share power, with a range of other politicians whose views fall somewhere between the two.
Relationships at Stormont deteriorated after the Brexit decision, which the DUP supported and Sinn Fein bitterly opposed. However, parties in the political centre also opposed any departure from the EU, thus leaving unionists in a minority.
The long hiatus at Stormont after 2017 was only ended last year, but the ill-will from that period of stasis remains.