Although the Bourbon Restoration engaged in a degree of purging and score settling, the Napoleonic nobility emerged out 1815 largely intact, albeit often demoted in status. Most of the Bourbon’s ire was directed at the apex of the Napoleonic aristocracy, the Princes and Dukes of the Empire. As with the Napoleonic nobility as whole, these were individuals were overwhelmingly military men such as the Marshalate, but there were some non-martial examples such as Cambacérès who was the Second Consul. However, the top of the Napoleonic pyramid were all men who owed their position to a personal relationship with the Emperor. Napoleon wrote to Cambacérès “I want no Dukes other than those which I have created or may create (...). If I make some exceptions with respect to the former nobility, these exceptions shall be extremely limited and shall only apply to historic names.”

Although the Bourbons executed Ney, they tended to be far more lenient to individuals who did not openly propagate a Bonapartist restoration after Waterloo. Although stripped of titles, these elites retained a sizable amount of their gifts and fortunes they acquired during their service to the Emperor. For instance, Davout retained some of his estate and the Bourbons eventually restored some of his titles despite the former’s unwavering support of Napoleon, even after Waterloo. Others such as Soult and Gouvion St-Cyr were able to regain very prominent positions within successive French governments.

One of the consequences of the Napoleonic system of coupling financial rewards with titles was that the corpus of the Napoleonic aristocracy was well-placed to marry into the old nobility of Restoration France. The result was a blending of the old and the new elite social groups within France. In addition, one of the foundations of the Napoleonic system was meritocracy (at least in theory) so there was a strong component of educated professionals within lower and middle strata of the Napoleonic aristocracy (the Barons and the Knight). These individuals were well-placed to expand their wealth and prestige during the Empire and became part of the foundation of the leading families of France during the nineteenth century. Although the Empire was infamous for its stifling court culture, Paris became an important social meeting place for these individuals and habituated them to the salon culture of the Restoration

Ultimately, the Napoleonic legend of French gloire outweighed their questionable loyalties for many elites for the French state. Although there were outliers who still maintained Bonapartist sentiments, much of this nobility recognized that Napoleon would not return again.

Sources

Bergeron, Louis. France under Napoleon. Princeton, N.J.: Princeton University Press, 1981.

Dwyer, Philip G. Napoleon and Europe. Harlow, England: Longman, 2001.

Natalie, Petiteau. “The Nobility of the Empire and the Elite groups of the 19th century - a Successful Fusion.” Napoleon.org. http://www.napoleon.org/en/reading_room/articles/files/nobility_empire_elite_arsenic.asp#ancre3

Woloch, Isser. Napoleon and His Collaborators: The Making of a Dictatorship. New York: W.W. Norton, 2001.

It's been too long since I read a great collection of essays on this subject - Napoleon's Legacy: Problems of Government in Restoration Europe - so this is not an in-depth answer. The work deals less with individuals and the aristocracy than the broader political transformation but it's well worth reading if this is a topic that interests you.

The core thesis of the book is that, accounting for disparities across the Continent, in general the Restoration monarchs were neither capable nor willing to turn the clock back. That is, they each inherited from the Empire state machinery significantly more sophisticated than that of the ancien regimes and, regardless of philosophy/ideology, the natural temptation was to make use of this. But you can't run this enlarged state without men with the right education and experience, which necessitated keeping on not just Napoleon's leading statesmen but a whole generation of officers and bureaucrats who had come to office under the Empire. As such there was far more continuity with the Empire than historians used to believe.

Hence when the Legitimists in France initiated the mass purges of Bonapartists, they did so in opposition to Louis XVIII, and their programme was far from complete. By the time the initial period of reactionary terror had passed, by 1820, it became clear that there was to be no return to the absolutism of the pre-Revolution monarchy and that many of the personnel and features of Napoleon's rule were here to stay. A similar dilemma faced the Restoration monarchs in Italy: most chose to retain at least some of the expertise that their bureaucrats provided; those that didn't (ie Piedmont) soon relaxed their reactionary policies. It was just more useful to have these people on side than against.

Those individuals that didn't 'make the cut' and were released from state duties tended to be the junior elements of the Napoleonic regime. Tens of thousands of officers, doctors, lawyers, etc were dismissed in France alone. Employment opportunities across Restoration Europe (particularly both France and Italy) were curtailed for many young and educated middle-class professionals who had made a home in the Bonapartist state. Ultimately many of them found their way into opposition parties and revolutionary secret societies in the decades post-Vienna.

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