There are so many things that seem off with what happened to Carl. Some said it was Chandler’s decision to leave the show because he’s going to college (which if that’s the case, then it’d be understandable) but after I read and check some articles, I found one where his dad said Chand was told to quick the show by Gimple only 2 weeks before his 18th birthday. He also said Gimple originally told Chand that he wanted him for another 3 years, but changed his mind and decided to kill him off as a “shock moment” in the finale (his dad also mentioned Chandler was hurt after he was told to leave?😢) According to the comics, Carl was supposed to be the last man standing. He was supposed to be the key part of almost every major plot line. Something seems off with him when he told Rick he wanted a “peaceful way. Not war” to make things work with Negan. This doesn’t sound like Carl at all! At first, I thought Carl was just going to run away as we saw him writing a note for his dad earlier. But in the last scene, we saw him at the end of the tunnel, reveals a bite on his side (which means it can’t be cut off. The only way he could survive is if he is immune) I thought Siddiq said "I carried him here" and then Carl says "that's when it happened," meaning that Carl had somehow been bitten in the sewer offscreen. But in actuality, Carl was bit in the woods when he was helping Siddiq clear those walkers two episodes ago. That's why he was staggering around Alexandria, not just because of Negan's grenades, but also because he was a day into a bite. It also explains why he was writing a note to his dad, why he stayed behind and offered himself up to Negan to be executed, because he knew he was dead already.
I don’t know what’s actually happening, if it was Chandler’s decision or Gimple’s. I don’t know if the show is playing with us and that Carl is immune. I don’t know anything. No one knows. All we can do is wait 😞