In this case the neighbouring countries arent great comparators. Population density has been mentioned elsewhere in the thread. Large swaths of the country is empty with the populace being very urbanised. Stockholm has a population density on par with London, and Oslo is about half of that.

Also households look very different in Sweden compared to it's neighbours. The average household size is among the lowest in the world with a very high variability (in particular in poorer areas where large family groups live together and were also disproportionally hit by COVID). That probably had an outsize effect as to why Sweden managed as well as they did. Social distancing and personal space is also pretty much the norm in Sweden even during non-pandemic times.

The Swedish CDC also says they believe they've fared worse than Norway and Denmark because the last few flu seasons were very mild in the country. Looking at the excess mortality numbers for the last few years that does indeed seem to at least explain some of the difference (although the claim has been disputed by their Norwegian counterpart).

It's also notable that Sweden tends to do a little worse than their neighbours through every flu season when it comes to excess death. Maybe COVID also just exacerbated that effect somewhat?

I think that the factors influencing COVID spread are so complex that it is impossible to disentangle how effective any political measures were in all but the most general terms.

In the end I think it mostly came down to luck, where those countries that managed to avoid clusters and super spreader events or more infectious strands early on fared better.