Why could Lucy and Edmund not return to Narnia?
I believe you mean Peter and Susan because Edmund and Lucy return in “Dawn Treader”. Peter and Susan learned everything they could in “Prince Caspian” that they don’t really need Narnia anymore. Peter does return with Lucy, Edmund, and Eustace for “The Last Battle”. Susan doesn’t return because she is “no longer a friend to Narnia”, as Peter states in “The Last Battle”. That basically means that Susan doesn’t care about Narnia anymore. She’s more interested in lipstick and what’s “hip” rather than Narnia, which she now believes is just a fantasy and a thing they did as young children. So far, all C.S. Lewis tells of Susan is that she lives in our world while her parents, siblings, and cousin, live forever in Narnia, but die in a horrible trainwreck in this world.
