The young crave excitement, lack empathy (it's to do with brain chemistry), have a huge sense of entitlement, despise their elders.
So they smash things up. Everything from bus shelters to social conventions. Some of which is good.
We've all been there, but we forget- or we cast a retrospective glamour over our youthful shittiness.
I didn't burn and loot high street shops, but I did things that were, morally speaking, just as bad. Bet you did too.
There's no need to bring poverty into the equation. The PM, the Chancellor and the Mayor of London used to be in a gang called the Bullingdon Club. Their schtick was to get very, very drunk, trash restaurants and assault passers-by. None of them was poor.
Usually there are restraints in place to keep youthful mischief-making within bounds- to keep the outrages small-scale and local. For some reason they just failed.
Why? Why now? That's the real mystery.