The French were thrashing the coalition forces for 2 years before Napoleon led a major campaign. Napoleon was a military genius, but what shifted the revolutionary wars in the favour of the French was the revolutionary goverments' innovation of total war - directing the entire economy and population of the nation towards the war with mass conscription and modern organisation. That would have happened with or without Napolean, and it was the social forces of the Revolution that made it possible for a Corsican nobody to even become a general in the first place.
Honestly the biggest argument for great man theory in the French Revolution is Louis XVI - if he hadn't been quite so indecisive and incompetent maybe the revolution would have fizzled out or been crushed instead of spiralling out of control.