The idea of marching in column came about as part of a series of reforms considered in the 1770s and 80s, after the French Army's desperately poor showing in the Seven Years' War. Other innovations included the corps system, a new appreciation for the power of massed artillery and horse artillery, the role of the skirmisher, and an early conception of the idea of the "nation in arms". The last was the idea of the Comte de Guibert who, while he did not foresee the levee en masse and the fervour of the revolutionary armies, did believe that it would be easier to achieve strategic objectives with large citizen armies motivated by patriotic feeling.

The concept of the column came about when Guibert and his contemporaries began to doubt that a rapidly-raised army of citizen soldiers could be sufficiently trained to attack in line, exchange volleys with the enemy, followed by the bayonet charge, all of which required extensive training in foot drill. The column, though, would take advantage of the herd instinct and mass men into a formation that was deep rather than long, thus providing the psychological impetus to close with the bayonet and provide the mass to smash through a thin line formation. It was generally expected, though, that the column would move into line as it approached the enemy and begin an exchange of fire, though in practice, officers almost uniformly did this too late or simply kept going. With a smaller frontage, the column was also easier to control and manoeuvre over broken country than the elongated line.

In practice, the column in the attack would be preceded by a thick cloud of skirmishers who would target the opposing battalion with individual fire, picking off officers, colour parties, drummers, etc., to disorder the enemy before the column hit. Column and skirmisher tactics played to the strengths of the large conscript army raised after the French Revolution, especially when backed by large quantities of artillery. A common form of attack was ordre mixte, where a veteran regular battalion of the old royal army would be paired with two battalions of new recruits, with the new battalions in column on the flanks to provide staying power in the event of a cavalry attack, and to deliver the final push with the bayonet, while the regular battalion marched in line and gave fire. After the Grande Armee professionalised again under Napoleon, the column was more of a manoeuvre formation than an attack one: at Austerlitz, the first echelon of battalions attacking through the centre on the Pratzen Heights moved from column to skirmish order at the run and chipped away at the coalition battalions until the next echelon came up in ordre mixte and chased them from the field.

Sources:

Paul K. Davis, Masters of the Battlefield: Great Commanders from the Classical Age to the Napoleonic Era

Paddy Griffith, French Napoleonic Infantry Tactics, 1792-1815