There are interesting ideas here. Personally, I find the War on Terror explanation a little far fetched. I think a more likely possibility is that movies started specializing.

In the decades before the Internet, cinema was one place where the average person who didn't buy dirty magazines could glimpse more skin than in everyday life. Then the Internet came along. Suddenly pornography was in everyone's home. Soon it was in everyone's pocket. Sexual desire became something you could very easily take care of, to your exact specifications, in private.

The one-size-fits-all portrayals in movies became gauche by comparison. And unnecessary. The public had infinite access to the sexual equivalent of gourmet food, so it suddenly seemed old-fashioned for the cinema to keep peddling stale bread.

Probably this also contributed to the me-too movement and the surrounding fallout over the sexualization of women in spaces where sexuality was now seen as being inappropriate. For example, the controversy over grid girls in racing.

A populace thoroughly satiated in private can afford to be puritanical in public.