The Chagos Islands had been home to the Chagossians, a Bourbonnais Creole-speaking people, until the United Kingdom expelled them from the archipelago at the request of the United States between 1967 and 1973 to allow the United States to build Naval Support Facility Diego Garcia, a military base on Diego Garcia, on land leased from the UK military in the British Indian Ocean Territories. Since 1971, only the atoll of Diego Garcia has been inhabited, and only by employees of the US military, including American civilian contracted personnel. Since being expelled, Chagossians, like all others not permitted by the UK or US governments, have been prevented from entering the islands.
literally searched your query into duckduckgo - https://en.wikipedia.org/wiki/Chagos_Archipelago
The Chagos Islands had been home to the Chagossians, a Bourbonnais Creole-speaking people, until the United Kingdom expelled them from the archipelago at the request of the United States between 1967 and 1973 to allow the United States to build Naval Support Facility Diego Garcia, a military base on Diego Garcia, on land leased from the UK military in the British Indian Ocean Territories. Since 1971, only the atoll of Diego Garcia has been inhabited, and only by employees of the US military, including American civilian contracted personnel. Since being expelled, Chagossians, like all others not permitted by the UK or US governments, have been prevented from entering the islands.
Read more of the Wikipedia article, you almost literally made it to the part where no one was living there prior to European arrival.