Headscratchers / Charmed S6E19 Crimes And Witch Demeanors

• Once again, the actions of the Cleaners don't really make much sense. Why does Darryl have to die when he wasn't the one who was at risk of exposing the magic? Sheridan recorded the video. Why couldn't the Cleaners erase or corrupt the video and erase her memories? Also, why would the risk of magic exposure end with Darryl's death? Finally, the Cleaners can't tell if someone is possessed by something?