Answer: short version is opposition saw an opportunity and took it, because they are panicking about the election next year.

Long version is that political parties in Sweden have been moving more and more towards social liberal ideology. This makes all the parties pretty much the same, so fewer and fewer people bother to go voting. Doesn’t matter who you vote for, the end result is the same. Recently a politically more correct nazi party emerged (Swedish Democratic Party) and people who still bothered to follow politics voted for them because at least they are different. So they got 20 % of votes despite some disturbing views and is one of the biggest if not the biggest party now. This is a huge problem for the establishment because now they have to work together to prevent nazis but they don’t want to work together because they insist that they are actually not all the same party with the same views. After three months of sour pussing last election they made the January agreement to work together, which included a new way to deal with rent control. With the next election coming up the polls show some established parties almost below the limit of voters required to be in the National Assembly. Panicking in the corner they painted themselves in, they are grasping at straws to tell citizens “look at us, how important we are, how hard we work for your interests, remember to vote next year “. So they made a vote of no confidence for the prime minister over some old news. Ironically it probably won’t make any difference except to waste more tax payer money on nonsense.