After Napoleon III annexed the Kingdom of Sardinia, Victor Emmanuel II, who had fled to London, established the Sardinian Exile Government with the help of the British.
Later, when the French annexed the remaining Italian territories, Victor Emmanuel II reluctantly became the leader necessary for the anti-French movement in Italy.
The reason was simple, the barefoot are not afraid of those with shoes, and Victor Emmanuel II, who had nothing left to lose, had the courage to fight to the death with the French.
In contrast, the situation was different for the other sub-state royal families. Although the French had taken their countries, they still nominally wore the crowns and received an annual pension.
Against this backdrop, everyone was very dissatisfied, but nobody had the courage to openly confront the French, and they merely engaged in petty schemes in secret.