Answer:
The 'invisible crime' that was prevalent in the 1950s when Miller wrote The Crucible was 'communist hunt' also known as 'McCarthyism'.
Step-by-step explanation:
In his essay titled 'Why I Wrote "The Crucible"', Miller hints about this 'invisible crime' that was prevalent in America in the 1950s. When Arthur Miller wrote the play "The Crucible" about the witch-hunt in American colony Salem, Massachusetts in 1692-93, at the present-moment America was dealing with McCarthyism.
McCarthyism, Communist-hunting, was similar to the incidents of witch-trials in 1692-93. After Soviet's first nuclear weapon test in 1949, the US government feared communist incursion.
Therefore, the correct answer is McCarthyism.