But why? I genuinely do not understand.

I thought this was film. I was so scared lmao.

https://en.m.wikipedia.org/wiki/Lucien_Olivier

I suppose he was of franco-belgian descent, but he was born in Russia, raised in Russia, died in Russia, and invented his salad in Russia as a chief of a russian restaurant.

Even the french agree: “Lucien Olivier est un chef russe d’origine franco-belge” - from Wikipaedia.

Also:

“Nationalité - russe”

Russians actually call russian salad “olivier”, after the guy who made it, but it was invented in Russia by a man that was born there, so I am not sure you can say it is French.