Does anyone have a clue why the airbase at Diego Garcia was built when the RAF was just leaving RAF Gan on Addoo atol in the Maldives?

Not enough ramp space? Gan is 5x3km and the runway is 8700ft.

Before the 12000ft Space Shuttle emergency runway was built in 1982, the original 1973 runway on Diego Garcia was 8000ft.

PS: Did you know that in the early 1970’s Russian Tu-95 “landed” at DG a couple of times? They performed touch-and-goes there.