Why did Prussia become a potential rival to Austria in the German Confederation after 1815?

After 1815, Prussia emerged as a potential rival to Austria for hegemony within the German Confederation due to significant territorial and geopolitical shifts resulting from the Congress of Vienna.31

The victorious powers tasked Prussia with defending Germany’s western boundary against potential French aggression. Consequently, Prussia acquired the Rhineland and Westphalia, including the industrial Ruhr district. This shifted Prussia's center of gravity from eastern Europe to western and central Germany, making it the only great power with a predominantly German-speaking population.23

Conversely, Austria’s focus shifted eastward toward Italy and the Adriatic, as it surrendered its western and southern German territories to gain greater geographic compactness. Furthermore, Prussia later gained a significant economic advantage by establishing the Zollverein in 1834. By creating a customs union that excluded Austria, Prussia secured a powerful tool for economic consolidation and political influence, effectively challenging Austrian dominance in German affairs.2145