“At some point we wanted to absolutely, definitively and clearly say, yes, that is Logan and he is dead,” Mylod explained, noting that he chose not to focus much on the body throughout the episode. The filmmaking choice is impactful as it gives viewers the same sense of uncertainty the Roy kids feel — the sense that if we can’t actually see Logan, he might not be dead. Mylod ultimately decided to cut to Logan when Tom (Matthew Macfadyen) put the phone beside his face while the kids attempted to talk to him. Mylod notes that this might be “the cruelest way” to confirm Logan’s death to viewers, noting that there’s “almost [a] kind of coziness of the fireside chat of having the phone up against his ear.”
Once the team decided exactly how they wanted to reveal Logan’s body, they had to figure out how to do realistic chest compressions without injuring Cox. Apparently, there are stunt doubles who are able to withstand the strong pressure involved in the motion. “Chest compressions, it’s a one-inch compression so it can damage your ribcage so we had a stunt person come in so that we could do those for real,” Mylod explained, calling the strategy for the shot a “rare cheat” in an episode that still contains a strong sense of verisimilitude.
Cox was still involved in the shot, though he only had to appear briefly. “I asked Brian to come in one day and literally to lie down for 10 seconds,” Mylod shares. “I’d lined it all up, I put a marker on the floor exactly where his head should be.” In Vanity Fair’s video, Mylod outlines which parts of the shot are Cox and which are the stunt double, who provided only the torso part of the image.
Source : https://www.slashfilm.com/1297185/succession-put-brian-coxs-head-on-stunt-doubles-body-to-film-logans-death/