Indian restaurants were historically called curry houses as a pejorative.
India has many dishes that one might consider a curry, but we have no dish called curry. The only use of the word curry in restaurants is to appeal to British nationals (and anyone they spread their culture to).
It’s an artifact of colonialism.
I also don’t understand why you think it’s virtue signalling. If anything, your appeal to “150 languages in India” is virtue signalling because you’re trying to make a benevolent justification for a word whose history you don’t understand. Also rich that you say “learn a little history folks” when you yourself clearly didn’t learn it in this instance.
Now, there is a word “Kari” in several South Indian languages but it’s used to mean spicy sauce or “kadipoda” which means spice mix, both derived from “black” in reference to the use of black peppercorns. The generalization into “curry” was one of colonial misinterpretation.
https://www.theatlantic.com/health/archive/2019/04/why-we-ca...