As a kind of benchmark, there have been local instances of rioting/civil misbehaviour at other times, like the time after those kids on the illegal scooter being killed in an accident after being 'chased' by the police-van (though it was affer they'd escaped from the attention of the police vehicle, just apparently before they'd stopped riding recklessly enough to get killed down the road). These things happen, occasionally, locally.
We've not really had a spattering of widely linked episodes, though, since the Duggan case (2011). There was yet another "police 'chase' antisocial kids, they die" (or was it just the one kid, this time?) shortly after the above episode, but it was a proper catalysis of an equivalent local incident plus zeitgeist, and probably 'helped' to stay in the public awareness by having overlapping news-cycles.
There are loads of little powder-kegs, which occasionally blow up (and perhaps draw attention to themselves if they cluster at all), but they seem to be just local 'breaking point' things or just happen to happen.
News-reporting 'artificial associations' aside, though, either the circumstances have changed to spark off the catalysis (we've had sufficiently advanced social-media for years now, and that probably inspired 2011's copy-cat rioting, so it's not like comparing post-Twitter with pre-Twitter/etc) a surprising amount of coincidental near-boiling situations have just happened to mature or there's more of an actual invisible hand in it.
There's a bit of coincidence. From what little I know, the Southend incident (not to confuse with Southport!) was more Brightonesque mods and rockers. And the ...Leeds one..? was a protest directly against a child-safeguarding 'raid'. Probably helped to enpower those who would (if I have them in order) find their own reasons to play up in Aldershot, Tyneside, Bristol, Stoke or Hull events (the ones I can remember), but you needed more than a nudge from the News At Ten. (I'm not judging the causes of the Belfast hotspot at all... There's so many established reasons why there'd be trouble there that you couldn't really designate a tipping-point cause without much actual argument between those applying their own critical eyes to the question.)
Also, it's equally worrying if this
is just the norm, going forward, for cliff-edge resentments to spiral out like a bunch of ping-pong-ball-baited mousetraps filling a room. Like we did, for a while, look like we'd get motorway go-slow protests until the end of time (initially as fuel protests), but of course we'd get such things superseded. (After quite a gap, modern motorway protests have stopped being "we want cheaper petrol" to "we don't want anyone to
use petrol"...
) The switch between "the police don't do enough [against Them]" and "the police do too much [against Us]" is perhaps a more straightforward transition that doesn't need a gap to arise between (indeed, they can overlap and tongue-and-groove quite nicely, thanks!), if that's what our near-future holds.
Oh, I'm out here on the edge. I can't tell you what the feelings and motivations are, on the ground. You'd be better asking me what I think of the potential for reavers to start rampaging cross-border and stealing livestock, than why certain inner-cities (and potential outer-suburbs) might attract prptests. That may or may not be a bonus from an overview basis, but would probably be better in the hands of someone who has more elementary sociological skills than me, as well.