> Maybe I've got a few blind spots there, but didn't Napoleon took power by a military coup against a nominal democracy
Coup yes, military kind of ( based on his military successes, but it wasn't executed by troops), against a nominal democracy - not at all.
However the Napoleonic Code Civil and the many reforms he enacted in France ( administrative, educative) which were also spread, alongside the revolutionary ideals, abroad wherever he conquered, significantly impacted Europe. It's generally accepted that the French Revolutionary and Napoleonic wars ushered the new era of nationalism, liberalism and political thinking ( including Marxism, because Karl Marx was inspired by the French Revolution and this type of event figured prominently in his thinking).
Pinning it all on Napoleon would be falling for the Great Man fallacy, but he certainly contributed a lot.