Warning: SPOILERS ahead for You season 4 part 2.
The identity of the Eat The Rich Killer is finally unveiled in You season 4 part 2, and the reveal is more convoluted than audiences anticipated. At the onset of the season, Joe Goldberg makes it to London on the tail of a woman named Marianne but under the guise of college professor Jonathan Moore. There in London, Joe meets a sundry group of London's most affluent, one of whom Joe begins to believe is framing him for the murder spree of the Eat The Rich Killer.
You season 4 part 1 sets up the mystery of the Eat The Rich Killer with a tortuous "whodunit" conception. While the body count continues to rise for London's richest, Joe's investigation breeds clues about who You's season 4 killer could be, and the murderer in question seems to be able to rival Joe in just about everything including intellect, incrimination, and the ability to remain several steps ahead. This was indeed cleverly purposeful, as You season 4 part 2 reveals a murderer of that magnitude would need to be particularly special in order to elude the obsession of Joe.
Joe Was The Eat The Rich Killer
You season 4 part 1 heavily suggests that mayoral candidate Rhys Montrose (Ed Speleers) satisfies all the requirements needed to be a comparable adversary to Joe, yet he turned out to be a red herring for the true murderer: Joe himself. Rhys seems to fit well with the set of characteristics that would motivate the murders in You season 4 part 1 - he distrusts the wealthy, he has an election campaign that needs to be protected from the debauchery of his shallow friends, and he is easily identifiable in motive when deaths occur. When Joe confronts and kills Rhys, only for another version of him to appear, Joe starts to realize that he was London's Eat The Rich Killer all along.
With his rival dead, Joe is forced to unpack the discovery that his suspicions about the killer and Rhys Montrose were incorrect. At first, he doesn't quite understand his predicament, but with the help of the hallucinated vision of Rhys, Joe came to know that he's You's Eat The Rich Killer and finds that he has been unaware because of breaks in his psyche. As it turns out, these states result in Joe living out whole chunks of his life unhinged and unattached from reality.
What's been happening to Joe is illustrated in You episode 8 where he is seen kidnapping and restraining Marianne Bellamy. Here it becomes obvious that Joe has detached himself as a coping mechanism for the disastrous line of destruction he continues to leave behind him. Marianne, who is one of a few returning characters in You season 4 part 2, tries to reach through to the Joe she remembers but is ignored by what is nothing but a shell of Joe Goldberg.
Why Joe Hallucinated Rhys As The Eat The Rich Killer
The talk of erotamania in You helps explain why it's Rhys specifically that Joe hallucinates. Known as a condition that involves a person falsely believing someone of a higher social status is in love with them, erotomania is said to be the cause of Joe's fixation on Rhys. It would seem that Joe obsessed over the celebrity in Rhys, culminating in the latter unknowingly becoming his serial killer alter ego. Instead of accepting his own flaws, Joe has been projecting his worst traits away from him and onto a spectral version of Rhys.
Did Joe Ever Really Know Rhys In You Season 4?
Based on what was established in You season 4's ending, it's apparent that Joe's familiar wit the actual Rhys Montrose was surprisingly limited. In the scene where he described Joe as person with erotomania, the vision of Rhys discloses that Joe had few real encounters with the candidate running for mayor and only imagines Rhys when he needed to compartmentalize his violent urges. Every instance that Joe and Rhys interacted, besides the few they shared at Simon's funeral, Ed Speleers' character was just a figment of Joe's broken imagination.
What Rhys' Presence Signified In You Season 4 Part 2
In order for him to deal with all that he has done up through You season 4, Joe dissociates and relies on an alter ego to personify his darkest thoughts and actions. Because Penn Badgley's Joe Goldberg already had it in his mind that Rhys had an evil within him that could rival his own, Rhys became the figure representing Joe's own immorality. After Rhys' actual death and the biggest break in Joe's psyche, the hallucination of Rhys served as the separate but darkest killer instinct that had always been a part of Joe in You.
Why Rhys Tried To Prevent Joe From Jumping Off The Bridge
The vision of Rhys goads Joe into accepting his deep-seated killer instinct in You season 4 part 2 - once Joe accepts that part of himself, they could become one and Joe would finally be free to live in his full truth. But Joe cannot agree to receive the most shameful part of himself and instead feels the best solution is to jump off the bridge. Despite Joe proving unsuccessful, Rhys pleads with him to reconsider in a bid to continue their unrestrained killing sprees.
Because Joe survives the incident on the bridge in the You season 4 finale and comes to find that his new love interest accepts his true nature, Joe decides that his best course of action is to absorb his killer instinct and become the person he tried not to be. By the end of You season 4 part 2, Rhys has disappeared out of Joe's perception, thus indicating that Joe has transformed into his highest self. Now that Joe is content with Kate Galvin and comfortable with who he is and what he has done, it is safe to say that You has yet to show Joe Goldberg at his most dangerous.