France gained much of its power early on by taking advantage of the chaotic period following the fall of feudalism. While many other nations were full of feuding nobles trying to seize power, France had already stabilized and was busy laying claim to land in other kingdoms. It's prosperity increased under the rule of King Henry IV. He promoted the growth of industries, especially textiles, and built up the French armada to a truly impressive caliber.
France flourished and prospered until the late seventeenth century. The start of its decline was marked by the carless spending and thoughtless manner of King Louis XIV. He entered france into many wars, severely depleting the army and naval reserves and lived so lavishly that he left the french treasury dwindling. However he also brought about a time of learning, art and music never again seen in the French Empire. This is unsurprising. His entire approach to ruling was, "Après moi le déluge" (Translation: "After me the flood"). He did not care what happened to france after he was gone, so long as he had made his mark.