2) & 3) Aztecs took gold tribute from their subject tribes and amassed it.
Spanish conquistadors looted the Aztecs gold.
Sir Francis Drake and other English pirates looted their gold in Spanish galleons.
British stopped being able to transport gold during World War I and II because german U-boats were sending significant fractions of Allied and especially British boats to the bottom of the ocean.
Seizing gold vaults have always been an universal war objective.
Politicians have achieved to control monetary systems by controlling gold.