> Or is Sweden more averse to questionable cases than the US?

Formally I think it is. A Swedish public prosecutor should not prosecute unless they “can look forward to a conviction”. So formally, they should not try a case where they are not relatively confident that the court will convict.

Also, Sweden doesn’t have a jury system. There are “amateur judges” (“nämndemän”). In the first court (“tingsrätten”) the case is typically heard by one magistrate and two “amateur judges”. But on appeal it’s typically three magistrates and two “amateur judges”. Finally, the court has to explain its reasoning in a written verdict. In combination this makes it harder to get convictions in complicated cases with circumstantial evidence.