I think this is missing the point of the original question, which is - why would a Mauritian feel "relief" at the return of a geographical territory which is extremely far from itself? The claims of the UK or the US are irrelevant to this reasoning.

Indeed, I would like to understand the answer to the above question better, since the only reason I can see is that Mauritius as a colony used to govern the islands, and that seems to have just been a convenience of the French that doesn't strongly justify any current claims of sovereignty. And since the UK were the ones to forcibly evict the Chagossians from the islands, it seems a double-injustice to "return" their land to another sovereign power which is equally at a distance from the islands themselves. Do the Chagossians support this claim by the Mauritian government?