I think you need to read this https://delong.typepad.com/kalecki43.pdf

Social democracy as far as it is instituted for the defense and advancement of capitalism will always run head first into the brick wall that is the investor classes market monopoly on investment capital, to advance the material condition of the working class is by definition to undermine the social position of the employer and investor class

Social democracy is historically a treaty of cooperativism between big business, labor and the government in favor of labor and capital, but this dynamic undermines capital in the long run inevitably leading to stagflation, investor strikes and state capture by capitalists who correctly recognize their social prestige is being threatened by a labor class that grows ever more confident with each victory