During summer, Swedes are spending as much time as possible outside (to make up for the dark cold winter months). Most offices are closed anyway, and unlike many other countries in Europe which have removed their previous limits, Sweden still has a 50 people limit on public gatherings and strict rules for how restaurants and bars can operate (for example, only table service, no bar service, even for outdoor venues). Amusement parks are closed. The authorities still ask people not to use public transport if they don't have to. Plus, people in risk groups (who don't have antibodies) are still asked to limit their interactions with others and to limit their mobility.
So considering that infections are happening mostly indoors, that Sweden nowadays has more restrictions in place than many European countries that locked down and then opened up, and that Swedes generally protect their personal space and don't get too touchy with others (in comparison to some other cultures), it's not a surprise that the numbers in Sweden are going down.
I'm happy about this trend. The way I see it, the country gets a second chance now to get things right ahead of fall/winter. Sadly, considering that the state epidemiologist and his team still are the same (and that he evidently mostly cares about telling everybody how great his strategy is/was), I guess they'll find ways to screw things up again.