I bet this has a lot to do with the Argentinean president.

Also of interest: https://en.m.wikipedia.org/wiki/Chagos_Marine_Protected_Area

"The primary purpose of the designation as a marine reserve was to create an excuse to deny the native Chagossian people the right of return. Unlike true marine reserves, the area is heavily polluted by the nearby military base, which is exempt from all restrictions imposed on the area. "