There is a concept called Solidarity, which Swedes take very seriously. If one employer chooses to not play fair by the rules of the labor market (which include negotiating with unions in Sweden) then other unions will show Solidarity with the one striking. The unions act with the mandate from the workers. They are not dictatorships.
Historically solidarity between workers is the reason why you only work 8 (instead of 16) hour days. Why workers have vacation days, sick pay, pensions and maternity leave etc.