TL;DR. My question: The following sources onfirm that despite Napoleon's industry and perseverance, he never refined his French to the level of a native fluent speaker.
So how did he succeed in France, especially were it more elitist from 1769 to 1821?
Optional Additional Information:
While at Autun, Napoleon had to learn French; as of yet, the future Emperor of the French could hardly speak the language. The effort did not go well. Napoleon found memorizing difficult, and his natural inclination to hurry did not do him well in the study of language. Worse yet, his French had (and always would have) a strong Corsican accent, a fact that did him no favors throughout his schooling. Still, after three months at Autun, Napoleon had learned conversational French and was able to pass his language exams.
... The opportunity to be an officer was reserved almost exclusively for the nobility and almost exclusively for native Frenchmen. To say that the system was elitist would be an understatement. ...
Worse yet, Napoleon wasn't even French! True, Corsica had become a French territory, but the French had a very low opinion of Corsicans (noble or otherwise), seeing them as just this side of barbarians. ... On Corsica, Napoleon's family was fairly high on the social scale. At Brienne, he was virtually at the bottom.
Add to that the fact that Napoleon didn't speak great French (and spoke it with a heavy Corsican accent), and it was clear that Napoleon was stepping into a situation that could prove to be very difficult. ...