Surely this can't be the blanket cause?
First, it's not a single reason but several going hand in hand. The main one, as far as I understand, is the sky-rocketing price of housing, coupled with little social safety net for which the US is well-known, produced a lot of homelessness that has not been addressed and ballooned. With that also came crime and drug abuse (that's not new: I've been there 10 years ago and was shocked by the amount of homeless people in the streets, and I live in Paris, which has its fair share of homeless people, so that's saying something)
The second main one is that racism, which has always been a thing, especially in the police force, produced some very high profile events (George Floyd) and high backlash against the police, perceived as racist and not being on the side of "the people".
There has been a big "defund the police", which resulted in less policing, police force demoralization, a lot of officers quitting. Coupled with the previous issue, a lot of small crimes happened, mainly perpetuated by poor people. It's important to note that due to the US history, being poor correlate strongly with skin color.
I don't really know if it's the fact that the people appearing the court were black and it was deemed racist or if the court were overloaded (probably an unhealthy mix of both), but at some point, shoplifting under a certain amount (was it $950? Somewhere in the $1000 ballpark) was changed from a felony to a misdemeanor. In practice, that means you could do that without fear of retribution, which predictably had awful results, and might be the disturbing videos you are talking about.
There you go, hopefully I didn't misrepresent the situation and didn't forget any other important factor, though I'm sure someone will correct me if I did.
https://en.m.wikipedia.org/wiki/2004_Pitcairn_Islands_sexual...
Yeah, I'll pass. Can you imagine how hopeless it must feel for kids here?