In this scenario France's economic situation is almkst worse than Weimar Germany at the end of the great war, political extremist are fighting in the streets, in 1932 a far left government gets elected and the military tries to coup the government, failing. During the chaos preceding the elections Napoleon VI was involved in the military operations against communist and fascist uprisings, becomig famous as a symbol of stability and resistance to all extremism (due to the fact that the military usually ignored fascist rallies and offered support to freikorps-like militias ). Italy aimed to gain Savoy and Nice from France during the chaos but the French unstable governament managed to repell the invasion, Napoleon VI also managed to invade Italy proper, creating the conditions for a cease fire.
His popularity was at its peak when the new government lost all legitimacy due to the institutions resigning in mass in protest and the military actively plotting to revolt.
Napoleon VI came back to Paris with his soldiers from his military successes in northern Italy and succesfully couped the government without blodshed. Napoleon VI then called a national referendum on the restoration of the French Empire under the Napoleonic dynasty. 60% of the votes where in favour, so Napoleon VI earned his title.
In the years following Napoleon VI managed to be up to Napoleon I's name, establishing his egemony over all of Europe.

Meanwhile, in the Soviet Union, Michail  Tukhachevsky is plotting to coup Stalin toghether with trotzkysts and bukharinists to restore party democracy. A soviet civil war will be ongoing as the poles and the french rush for Berlin, Mussolini is hanged by partisans and Horthy gives the hungarian kingdom to Napoleon VI's daughter to ensure future expansion and protection.

This scenario is not meant to be too realistic, I hope you like it.

Queen of Hungary Marie Clotilde Eugénie Alberte Laetitia Geneviève Bonaparte on the left, Emperor of the french Louis Jérôme Victor Emmanuel Léopold Marie on the right.

Light blue states are french principalities/occupation zones! Borders inside France are highly autonomous regions inside the french empire.

Napoleonic Hungary in the 20th century