The French Revolution and the Napoleonic wars profoundly shook Europe. The French Revolution was seen by the European great powers as both threatening and, increasingly as it progressed, morally repulsive, but at least it had largely stayed confined to France. From the perspective of elites, Napoleon's conquests were even worse because everywhere the French armies went the traditional order of society was overturned. France may have been the greatest economic beneficiary, but Napoleon's Italian, German, and Polish subjects (among others) also had their first taste of a society in which one's status was not defined by birth. The kings and nobles of Europe had good cause to fear that the way of life they presided over, a social order that had lasted for roughly 1,000 years, was disintegrating in the course of a generation.
Thus, after Napoleon's defeat, there had to be a reckoning. Only the most stubborn monarch or noble thought it possible to completely undo the Revolution and its effects, but there was a shared desire among the traditional elites to re-establish stability and order based on the political system that had worked in the past. They knew that there would have to be some concessions to a generation of people who had lived with equality under the law, but they worked to reinforce traditional political structures while only granting limited compromises.