The reason for Sweden's rather hands-off approach compared to other European countries was summed up rather well by lead epidemiologist of the Public Health Agency of Sweden, Anders Tegnell, who said in an interview with CNBC:
My view is that basically all European countries are trying to do the
same thing — we’re trying to slow down the spread as much as possible
to keep healthcare and society working ... and we have shown some
different methods to slow down the spread, [...] Sweden has gone
mostly for voluntary measures because that’s how we’re used to
working, and we have a long tradition that it works rather well.
This tradition of 'laissez-faire-ism' that Tegnell talks about was explored by Johan Norberg in his 2013 essay How Laissez-Faire Made Sweden Rich. This is quite long but well worth a read. Notably, Norberg argues that rather than Sweden's economic and social successes being a result of the SAP "managing to tax, spend, and regulate Sweden into a more equitable distribution of wealth—without hurting its productive capacity", Sweden's greatest successes both economically and socially "took place when Sweden had a laissez-faire economy".
Sweden's approach to the current pandemic, then, would seem to be influenced by the political traditions of its past. I should note that although Tegnell is hopeful that the current strategy will be successful, he doesn't rule out the implementation of more stringent measures should the data suggest that the laissez-faire tactics are not working.
As far as social factors that have influenced Sweden's response go, one such factor is how sparsely spread its population is. This article from Our World in Data notes how Sweden consistently ranks near the top of metrics related to single-occupant households, and the country also ranks 50th out of 54th for Population Density amongst other European countries.
It is likely that another factor has been the reluctance of the government to negatively affect the economy more than is required. For example, although taking a hands-off approach with regard to restricting personal liberties, it has taken a far more active role in ensuring the continued functioning of business, and on March 27th announced that it will guarantee 70% of bank loans provided to companies that are experiencing financial difficulty as a result of the pandemic.
In conclusion, Sweden's response so far seems to be a combination of the reluctance of Swedes to accept restrictions on personal liberty - note the outcry by opposition parties when a proposal to rule by decree was announced, a tradition of past laissez-faire approaches, and distinct social factors that will potentially help provide a natural defence against the virus.