Malmö is too complex to have any kind of single-factor explanation, certainly including "multiculturalism".What are cases of success ?... What are cases of failure ? What is the rough ratio of success to failure
Here is a case of failure (Malmo , Sweden)
“I think they just shot someone right across from my balcony,” my friend told me. The gunshot rang out even as we were texting about another recent act of violence here in the Swedish city of Malmö—a car bomb that went off in a residential area close to my home. Acts of violence occur so...quillette.com
Multiple cases of failure are related to the breakdown of empires (for example Austria Hungary) or even countries (Yugoslavia)
The difficulty lies in defining "multiculturalism"
Mulitculturalism is defined as the presence of, or support for the presence of, several distinct cultural or ethnic groups within a society.
The key point here is "distinct" , i.e. not integrated with the mainstream culture of the country..... As always it is difficult to define such concepts precisely... For example having a different diet is "not it", whilst not speaking the country's official language "is it"..... Importing different sets of customs that do not align with the country's traditions and core values would be "it" as well
The elephant in the room, if that's still a thing even, is that it is Sweden's "southern gateway" and has a proportionally large immigrant population. But we all knew that since twenty years or more.
But otoh one problem isn't immigrants per se, but that Sweden doggedly (and certainly with some good arguments as well) continues to maintain a distinctly high-wage, high-skill labour market. Entry-level jobs requiring no or little qualifications hardly exist. It's nothing like Germany, which has Europe's largest low-wage sector. This has effects for how and when immigrants can successfully enter into the national labour force, and doing that is a know key to integration.
What no one so far can explain is why the sudden, massive upsurge in violence? Yes, there has been gangs and drug dealing for quite some time there. That's hardly unique among the rougher cities of Europe. Just the recent upsurge in violence is.
Sure, Sweden there are plenty of privately owned weapons in Sweden, it's one of the better armed countries in Europe. But again, it's not unique. And besides, it IS Malmö that sticks out. The two other major cities, Göteborg and Stockholm, have declining violent crime rates. (And lots of immigrants too, for all that matters. Göteborg has been the Swedish Violent Crime Capital for some generations too, only to suddenly be overtaken by Malmö). There is an aspect to this that there is substantial illegal imports of firearms and explosives, military grade, from the Balkans (former Yugoslavia). That's where a lot of it comes from.
What does get commented on by police, sociologists et al. trying to get their heads around the situation, is that there is an apparent vicious cycle that started a while ago, has escalated, the young men involved in this kind of alternative criminal life-style in the underprivileged neighbourhoods are caught up in it, and – interestingly – they are not just being killed, but are sounding the alarm themselves over the situation, which has developed into something they did not expect, did not want, but have no way of getting out of.
What police describes is a situation where "gangs" is a bit generous, since that implies a certain formality and hierarchy. These are more loose sets of groups of friends and individuals, young men on the margins of society, who are engaged in fairly petty criminal activity, but has escalated violence to a level where deadly forces is the first recourse, weapons and explosives abound, idiotic tiny slights (sometimes imagined, someone looked at someone else's girlfriend, maybe, the wrong way) are met with massive disproportionate and deadly violence. Deadly feuds are entertained where the parties no longer recall the reasons, except the body of the latest mate has to be avenged by whacking one of the other group. And the people involved in this realize that it is super dangerous, deadly, shitty survival prospects for everyone, and yet they are unable to end the cycle. It is also then being fed by the fact that since propensity for deadly violence has become a way of climbing a prestige ladder. Even younger newcomers can quickly establish themselves by being even more outrageously prepared to just kill some dude they don't even know because reasons y'know... And so they have escalated the vicious cycle even further.
That does of course imply a massive policing problem. And that would be the case. Swedish police has been massively re-organized while this trend was getting started, and it has completely failed to be either present enough to avert anything, or good enough at catching the killers to make it stop. The gang-warfare now can continue because the police is unable to get inside the circle of information of who is killing whom why, and as a consequence the spiral of violence within these marginalised groups of petty crims continue. If you kill the "right" kind of person in certain neighbourhoods in Malmö, you will almost certainly get away with it.
However, for perspective, while this is all bad, and historically new to Sweden, it is not exactly historically new. It is the kind of stuff that retrospectively gets mythologized, and not necessarily that far in retrospect: