Why?
A couple of posters here have gotten close, but no one actually seems to recognize it explicitly.
Robert A. Heinlein did.
The why is that then you own the Moon’s enormous energy of position.
Heinlein defined a weapon as (paraphrasal) a device that focuses destructive energy on an opponent.
Heinlein’s “Loonies” put the two together, as can whoever lays claim to the Moon 1st...
That’s the short term view. The long term survivability of mankind is the long term view. :-)