The original strategy was herd immunity. The argument being made was that Sweden was gonna get infected anyways, so better to get it out of the way sooner rather than later, while protecting the at risk. And this would reduce economic harm as well.
However, the Swedish decision makers seemed completely unaware of asymptomatic carriers, which led to the at risk (largely old people) being heavily exposed anyways due to the asymptomatic younger workers around them infecting them.
Further, the Swedish people, reflecting normal human behavior, shut down economic activity anyways.
The result was a slight linear short term economic benefit but an exponential, potentially long term, downwards public health situation whose economic effects itself will likely dwarf the direct economic benefit anyways.
So now that their plan has failed both in concept and execution they are changing their story saying that it was a Swedish cultural thing, where they trusted individual Swedes to take personal responsibility, because of the exceptional Swedish character.