Why was there so much gnostic themed media in the late 90s and early 2000s?

>the x files
>dark city
>the matrix
>the truman show
>donnie darko
>evangelion
>serial experiments lain
>final fantasy vii
>deus ex

I could go on but I think you get the point. The trend seems to have sprang up out of nowhere for no obvious cultural reason and then disappeared after 9/11. Why is that?