Sweden does have an increased mortality, but the theory behind the policy is that the disease is more or less bound to spread through at least half of the population, and that too stringent action simply pushes the problem ahead. The Imperial College study that changed Britain's policy says pretty much the same thing - as things stand, there is a pretty broad scientific consensus that you can't really stop the spread for good without vaccine or some new medication. The argument for lockdown is that it can slow the spread down, so the health care system isn't "overwhelmed", but in essence no-one seems to believe you can actually prevent most people from being infected.
If any of this is true remains to be seen.