Feminum Mystique

I recall the Nazi occupation squad overrunning paradise Island, and capturing the Amazons, who are apparently a little rusty in their defensive skills after 5,000 years of frolicking in their togas and munching grapes in the Sun. ( among other things ) What I don't recall is how did the Amazons fail to lose all their powers once Man had set foot on the island, thus voiding the Pact of Hera, which makes them all super-powerful and immortal as long as Man never sets foot on their island??