it has a lot to do with a small bunch of creative people vibing off each other and starting labels. these types of scenes abound...same with early detroit (i am not comparing qualitatively, so no one even start...)...it was literally a bunch of friends working off each other. then it blew up.
you know though, not to be too patriotic or anything, sweden is the world's 4th largest exporter of music...sweden IS disproportionately represented in a lot of types of popular music...
...i would say this has something to do with the fact that it's basically impossible to be poor there (at least compared to the US or UK)...so you can be a starving artist and not really starve at all...