Catherine the Great ruled Russia in 1776. And she was German.
Prussia was a Germanic state. The King of Prussia was the Emperor of Imperial Germany, AKA the Second Reich. Nothing the least bit Russian about that.
European aristocrats shopped their children around, especially their daughters to try to make the best alliances with countries that would enhance their fortunes and their country's defense. She wasn't liked very well when she first married and came to court, but she eventually overthrew her husband, took the reins of power, and proved herself a great asset to Russia.