The Wikipedia article, both the Swedish and the English version, is fuzzy about the details how it worked, they took the company’s own money and use that to buy the company’s shares by forcing them to sell by equity issuance. Goal was to take over private companies and create socialism.
Social democrats were reformist but became radicals during the leadership of Olof Palme. This was not the only one radical thing that they did, another was the famous Pomperipossa taxation where some Swedes payed more than 100% in taxes. This led to other Swedes leaving the country, like the famous movie maker and director Ingmar Bergman.
As I wrote in another comment, this had disastrous consequences for Sweden, large companies left and we went from a consensus culture around business and politics (Saltsjöbadsandan) to a something much more antagonistic.
This radicalized the right wing in Sweden to become neoliberal for many decades to come, which led to other negative consequences.