I can’t figure it out either.
Does “the sad tale of hype fanning” fear that “modern cryptography was slain?”
Or is there a “sad tale of hype” that is currently “fanning fears” that “modern cryptography” has been slain?
Or is it “the sad tale of hype” itself that was slain?
It’s such a textbook example of a poorly-constructed sentence, it’s hard to believe it was written unintentionally.