But did Clinton know Lewinsky/someone was keeping the blue dress and had DNA evidence?
ie. I don’t doubt that if they thought they could get away with it, they could have Lewinski killed, but what stayed their hand?
I'm sure they did. You must recall this all goes back to the lawsuit filed by Paula Jones. Both sides would have had discovery and I believe that was how Lewinsky's name wound up in the media - except the media was stonewalling until Matt Drudge leaked the story.
I don't doubt that Tripp urged Lewinsky to tell the truth under oath and that included saying she still had the blue dress with Clinton's juice on it.