Why did the power of princes increase in Germany, while for the power of emperors, on the contrary, weakened?

For the reason that the power of the emperors was weak. There were too many pretenders to the throne. In the country itself, there were constant strife. The big princes tried to expand their power even more. Thus, the power of the emperor gradually weakened. For the same reason, the German lands were divided until the end of the 19th century. Even in the second half of the 19th century, there were more than 30 German states! It was only during the reign of Bismarck that Germany was finally able to unite into a single state.