The scene between Luke and Leia occurred late into The Last Jedi‘s runtime, with the fans waiting nearly two full movies to see the siblings reunited onscreen. While it wasn’t a long scene, it was enough to warm the hearts of the galaxy. With The Resistance backed into a corner on Crait, Luke suddenly appears to distract Kylo Ren, and allow the surviving Rebels to escape the salt planet. But first he visits with his sister, and their bond over their mutual loss in Han and Ben Solo. He then departs, and eventually perishes from the exhaustion of Force Projection shortly thereafter.
Article source: https://www.cinemablend.com/news/2467777/star-wars-the-last-jedis-most-heartwarming-moment-was-actually-unscripted