Like how exactly? If they had gotten crazy luck with a benevolent king that decided to bestow them rights? I'm struggling to think of a case where subjects became citizens with rights without either violence, threat of violence, or the sovereign getting scared of violence elsewhere. The French Revolution made many of the liberal reforms across Europe possible precisely because many rulers were deathly afraid of getting guillotined.
The reign of terror and wars happened after most of the nobility voluntarily gave up their hereditary rights. Even after the storming of the Bastille there had been very little real violence.
This is some weird revisionism. The Reign of Terror was until the Fall of Robespierre, July 1794. The Armée des Émigrés was still going strong and represented nobles actively fighting with France's enemies to destroy the revolutionary regime. The Vendée uprising was facing brutal suppression at the same time, but also existed and had local nobles participating.
Voluntarily is a massive stretch. Even more so when you consider that many that returned after the Restauration tried to get "their" lands and titles back - so it was only the threat of violence that made them abandon everything and run.
It isn't revisionism at all. The August Decrees happened in 1789 ending many of the privileges of the 1st and 2nd estates and by 1793 they were amended to turn land over to peasants for free. This was all before the reign of terror started. The nobles and clergy that participated in the National Constituent Assembly were practically racing to be the most forward thinking, the proposal to end feudalism came out of the Club Breton and was proposed by the Duke d'Aiguillon.
The Vendée uprising like many such uprisings was sparked by the Levy Decree(levée en masse) which was a response to the Girondins stirring up a stupid war for "national unity".
