Social democracy is the “final stop” before full-on fascism. It’s basically a tacit admission by the bourgeoisie that a socialist revolution is drawing near, and they need to appease the workers by whatever means necessary. Social democracy can also exist, feasibly, primarily via imperialism. The reason capitalism is able to provide such a robust welfare state is through the impoverishment and ruin of other countries. As I understand it, it is for these reasons that Stalin (correctly) calls social democracy “objectively the moderate wing of fascism.”