What I mean is that, Why was it Prussia that came to dominate Germany and not more well established regional powers such as Saxony, Bavaria, Hannover or Hesse?
If I remember my German history Prussia was a minor kingdom until Frederick the Great's conquest of Silesia in 1742, and the subsequent acquisition of Polish territories in the 3 partitions of Poland (1772-1795). These two pushed Prussia to become the 2nd most powerful German state after Austria. Silesia had iron, silver, coal, and over mineral wealth. More land meant more people, and hence more taxes.
Without the conquest of Silesia, Prussia would have remained a small German kingdom. (And thus may not have been invited to the Partitions of Poland.)
Frederick the Great was able to conquer Silesia because his father had nurtured a formidable army and an efficient government.