Why did Britain become a superpower? We might be able to use some of the same reasons here, i.e. France goes the same way as the HRE and finally breaks up. Brittany is the most powerful of the surviving states and colonizes large chunks of North America, becoming rich. Later, the Industrial Revolution also begins in Brittany.
Of course, Brittany is a pretty small area. This might require a great deal of luck/butterflies/ASBs.