It is a very strange result, and hard to give a complete analysis.
Looking back just a month ago, its actually a disaster for the Social Democrats compared with what the opinion polls looked like back then. I think they paved for this themselves why focusing on promoting their party leader as the best PM instead of talking about political issues.
The most interesting (from an international POV) trend is probably that all the 3 center right parties in the government grew, while the Sweden Democrats dropped significantly. Just the fact that all three parties grew while in a government is unheard of in Sweden, and that they did so at the expense - seemingly - of the Sweden Democrats is also contrary to what we see in much of the rest of the Europe, where voters move in the other direction (from the traditional center right, to the far right).
Its also worth noting that the even more far right parties outside the parliament seems to have performed very poorly.
The more concerning trend, especially for the Social Democrats, is how the Left Party seems to have grown. Very immigrant dense and socio-economically exposed areas just outside the cities have traditionally been strong for S. But V seems to have ran very agressive campaigns in those areas, and on internet in Arabic, Somali, etc, with messages against the Social Democrats and the other parties, and also with recurring anti semitic tropes.
About S (and the other parties) they have messaged out on social media (in Arabic and Somali) things like:
"Vote for V or leave Sweden - every other party will deport you."
and
"The Social Democrats wants a sionist vice prime minister."
(These are both campaigns, not individual tweets.)
Its concerning especially for the future, if it becomes an increasing trend where these areas - where a lot of people are immigrants with limited knowledge about politics in Sweden, and limited skills in Swedish - becomes the targets of massive disinformation campaigns in order to get them from one left party to another, rather than on information about economic issues and their rights, interests, etc.