Sweden is one of few countries that reach the United Nations goal stating that countries should give one percent of their GNP as foreign aid. According to the reports I could find it is currently the largest giver of foreign aid in the world, with regards to it's economy and population.
This wasn't spontaneous. It happens every year although the amounts changes as we see here.
I read your article and surfed around for better information, but couldn't find much. So here's a bunch of conjecture, feel free to skip it. Link me better stuff if you find any.
First, you can't go giving away other peoples money and call it 'charity', or measure it against actual charitable activity.
As far as I can tell, the 'best in the world' status relates only to the fact that they 'give' (redistribute) a higher percent of GDP than any other nation. They still sell or give arms to despots (as even your article points out). Much of their aid is in the form of government purchase of Swedish products, then given away, which surely leads to some crony backroom deals with industry leaders, as all protectionist measures do, you know, pork barrel politics.
My assumption, and the reason that it's easy to smear, is that people with power aren't angels, and taking money from locals to deliver off to some foreign land may be for reasons that are less than scrupulous or benevolent, that there is inherent conflict of interest (conditions for corruption) in every government expenditure.
Of course all such matters will be offset by very visible donations to the humanitarian effort of the day, in this case, Syria. Whatever form their aid to the 'refugees' takes there, unless it's going straight into the mouths of the needy, you'd better bet some of it will be redirected into winning the fight.
This wasn't spontaneous. It happens every year although the amounts changes as we see here.