Order 66 is one of the weakest scenes in an already weak film. The Jedi are way too easily dispatched, and don’t fade when they die. Vader can’t “hunt down and destroy the Jedi Knights” if all of them are dispatched this easily.
I mean, they had an explanation for why they don’t fade. Qui-Gon was the first Jedi to learn how to become a ghost, and he passed that information down to Yoda and Obi-Wan.