It is no secret that Star Wars: The Last Jedi is full of heated debates and questions. It’s also no secret that the movie does have a few plot holes (most movies do). Rian Johnson is more than happy to help answer some of the questions and do his best to close some plot holes in interviews. In true Johnson fashion he has talked to IGN to explain a part at the end of the movie that has raised questions from many fans. This should go without saying, but SPOILERS ahead.
At the end of the movie, we have a showdown between Kylo Ren and Luke Skywalker. This is the showdown we were all waiting for since Star Wars: The Force Awakens. The question many fans have though revolves around Luke’s weapon of choice: Anakin’s blue lightsaber. Many fans have asked why Luke didn’t use his green lightsaber. Why did he use his father’s? I knew part of the reason was to be a clue to us, the audience, that this was not really Luke. However, here’s Johnson’s explanation:
But what about the lightsaber splitting in two? There's no way Kylo wouldn't have noticed that, right?
That makes sense. I hadn’t even considered that due to the flash of light Kylo wouldn’t have been able to see the destroyed saber, especially since Rey is already gone by the time he wakes up. It also makes sense because Luke knows about Kylo’s obsession with everything Darth Vader. By seeing his old mentor whom he had deemed a failure using Vader’s old lightsaber, Kylo’s anger levels would skyrocket. Thank you, Johnson, for helping me understand this a bit better. Does this help solve your quandaries about the final showdown for Luke Skywalker?