The idea of a succesion of german empires was a nazi propaganda tool.

The Bismarckian german empire of the late 1800s was very much opposed to any idea that they continued any german traditions from the holy roman empire, which they thought was backwards and ancient.

Hitler used it to bring back memories of glory, Frederick the Great was dressed in new clothes and was celebrated as a german nationalist hero, when infact he was more a prussian nationalist. Hitler wanted to give a sense of historical continuance to the newly formed Germany, even if in the process perverting the prussian history.

Source: Clark, Christopher. 2006. Iron Kingdom: Rise and fall of Prussia 1600-1947. Penguin