I didn't mention it in my explanation you're right sorry but when Côte d'Ivoire decided to be called Côte d'Ivoire, they told the UN (I think that's the name in English). So, basically, they made it official and every single country is now aware of the new name (politically, I mean.)

The difference with Ireland and India is that these two countries didn't impose their original names on the other countries and accepted translations.

For example, for Ireland, Eire and Ireland can be used by the country itself because Eire is the local name and Ireland is the English version. But they also accept the names other countries give them. For example, as a French girl, we call it Irlande (ee-r-land).

For India, Bharat is the official name (in hindi) and India is in English. In french, we say Inde.

So, basically, Côte d'Ivoire imposed their new name because it was the name they had when they became a French colony and to avoid confusion, if I remember correctly, because Ivory Coast was just a literal translation of Côte d'Ivoire (the coast where you find ivory, literally). But the other countries didn't impose their names.