I think it’s an artifact of how widespread the contagion was when restrictions were implemented. Stockholm has about twice the death rate as Västra Götaland, but lower case incidence. This is all plausibly explained by the observation that the epidemic started in Stockholm, and there were already hundreds of cases there when restrictions were enacted on the 18th of March. Protective gear was in short supply, supply lines were disrupted and the spread spiralled out of control. Other parts of Sweden had a far smaller case incidence at this point, so the restrictions were more effective, and by the time it became widespread in, for instance western sweden, supplies weren’t as scarce, certain lessons had been learned etc.