For this answer I will be referencing Francis Hare's pamphlet on Bouchain, Rich Wilson's 'Louis XIV', and Jamel Ostwald's 'Vauban Under Siege'.

To some extent, it might be something that occurred from the reign of Louis XIV, the 'Sun King' of France, who ruled from 1643 to 1715.

During this time, he turned France into a cultural hub, a pioneering state of both science and fashion. In German, Italian and Spanish courts, the predominate styles and dress quickly started to emulate those of the French. Whether or not this is due to the political predominance is up for debate; regardless, during this period, Frenchmen began to regard themselves as the predominate nation of Europe. They were one of the most powerful states in the world.

It is extremely important to point out that the French Army really was simply incredible. With the aid of skilled commanders like Vicomte de Turenne and Sebastian de Vauban, Louis XIV was able to develop a modernised, sophisticated, organised army that could defeat other armies in the field, and also besiege and hold major fortresses. During the War of the Spanish Succession, the extremely numerous armies of the Grand Alliance were held off by the French consistently, despite several brilliant set-piece battles by the British and Habsburg commanders.

The French Officer Corps developed a sense of 'elan'; it lacks a proper English translation, but it is centred around forward action, bravery, daring, flare, and even a bit of style. Due to the aristocratic nature of the leadership of the French Army, this bleached into the Courts - soon, the large nobility of France saw themselves as more dashing and brave than their foreign counterparts.

Whether or not this period of French predominance is the direct cause of any perceived 'snobbery' in the modern conception of the French is ambiguous; what it certainly meant was that France developed a very real sense of national superiority that is found even in the literature of the revolution.