In Violet Evergarden, Gilbert is a bit like Schrödinger's cat. Schrödinger's cat is an experiment in physics where a cat and a flask of poison are placed in a box. The bottle of poison can break open at any time and kill the cat but until the box is opened, the cat can be thought of as simultaneously both dead and alive. Because Gilbert's body was never found, many people presumed he was dead with Violet being the only one who believed he was still alive. That was how the anime series ended with Violet continuing to live her life whilst still believing that Gilbert had survived the explosion.
In Violet Evergarden: The Movie, it's revealed that Gilbert is still alive and teaching children on an island. At first, Gilbert refused to see Violet, the guilt making him too ashamed to even face her but after reading her letter, the two finally reunited. Gilbert being alive is a bit of a contentious subject. While the series ended on a happy note, would it have been better, story-wise, for Gilbert to have died or never to be seen again?
Why Gilbert's Death Would Have Worked
Violet had never known anything but violence in her short life. After the war ended, she wasn't quite sure how to function because she had always been living according to other people's orders. Gilbert had been ordered by his brother to treat Violet like a weapon but he had strived to treat her like an ordinary girl. Just before the two got separated, the last order that Gilbert had given her was to live on. At first, she wasn't quite sure what that had meant but through her interactions with clients as an Auto Memory Doll, Violet started to understand.
Violet Evergarden is set in the aftermath of the war where those who were left behind, -- the soldiers' families -- and those who survived -- the soldiers -- had to learn how to deal with the grief and tragedy that came from the war. Every episode had Violet slowly putting herself back together after the war ripped her apart and learning how to be human again. Through her interactions with clients and her letter-writing, she was able to understand emotions and most importantly, come to terms with her own grief and love for Gilbert.
Violet's emotional journey has always been about learning how to live her life as her own. Violet was never really as robotic as she appeared to be but all of the trauma and violence that she endured forced her to suppress her emotions to the point where they were deeply buried. She started to understand all of the different forms of love such as the love between siblings, the love between a parent and a child, and even between romantic partners. When Gilbert's mother told Violet that her son was alive within her heart, it was a reminder to her that those who were gone were never truly gone.
At the end of the series, while Violet was still adamant that Gilbert was still alive since his body was never found, she had found another purpose in life. Her smile seemed to indicate that she would be okay in the end despite not knowing the outcome of Gilbert's fate. It would have made perfect sense for Gilbert to not return from the dead because all he had ever wanted was for her to live on and she had fulfilled his wish. While fitting, the problem is that Violet had never accepted the notion that Gilbert was dead. She was still, in essence, stuck in the past so her final arc feels incomplete in a certain way.
Why Gilbert Being Alive Brings Closure
Violet was despondent and despite coming to terms with her feelings for the major, she had never stopped missing him nor given up hope that he was alive. Although Violet realized that she could live life as a human, there was a heavy shadow of grief and sadness that hung above her. It seemed like she was never fully present and was only just barely surviving. Gilbert in this limbo of the Schrödinger's cat was hurting her more than helping her. As she told Gilbert's brother, as long as she was alive, she would never forget Gilbert.
Any time she heard the news of Gilbert, she lit up visibly and she seemed to come alive. Gilbert's words of "I love you" had been a guiding light for her. It had been the push for her to work as an Auto Memory Doll because she wanted to know what love meant. When she finally did, it was only right that she say those words to him, bringing her arc to a full circle and giving her the happy ending that she deserved.
Did Gilbert's return from the dead ruin Violet's emotional journey as a character? Not really. Although the ending of the anime series suggests that Violet seemed ready to live with the uncertainty of Gilbert's fate, the beginning of the movie says otherwise. The movie acted as the final piece to her healing; the series followed Violet as she learned how to be human and the movie gave her the opportunity to be human with the person she loved.