People knew their fellow Swedes, many times with family links going back generations.
There are a lot of things you can do in a high trust society, that do not work in a society without that level of trust - for example, generous welfare benefits where you trust your neighbors not to exploit the system.
Some studies have found a negative relationship between ethnic diversity and social trust [1], but it is difficult to have discussions about this since it is such a sensitive topic. And of course it is not the only factor.
People knew their fellow Swedes, many times with family links going back generations.
There are a lot of things you can do in a high trust society, that do not work in a society without that level of trust - for example, generous welfare benefits where you trust your neighbors not to exploit the system.