Spoilers for Star Wars: The Last Jedi.
Speaking with Entertainment Weekly, Johnson revealed why Luke had to die:
“I think the hero’s journey of Luke Skywalker concluded in Return of the Jedi. This [trilogy] is the hero’s journey of Rey, and Finn, and Poe,” Johnson explained. “The [ongoing] story of Luke is one that has to play in tandem with that of Rey.”
The former Jedi Master had exiled himself to Ahch-To, the "most unfindable place in the galaxy," where he had cut himself off from the far-reaching Force.
He had not only abandoned the Force, but the Jedi way as well, the grizzled former Jedi criticizing the Jedi of old — specifically those of George Lucas' prequel trilogy — saying the space monks had become deified and mythologized, having lead themselves down the path of their own destruction.
A path that gave rise to Darth Sidious and Darth Vader.
After an exchange with an old friend, Luke later makes his way to salt planet Crait to lend an assist to his sister — Resistance leader Leia Organa — and his allies in the dwindling rebellion, squaring off against his nephew and former student Kylo Ren.
But it was a ploy: Luke had never physically left Ahch-To, instead Force projecting himself to another part of the galaxy.
It was a move that left Luke depleted but at peace. Overlooking a pair of twin suns, Luke Skywalker vanished into the Force.
“I had huge hesitance. I was terrified," Johnson admitted. "It was a growing sense of dread when I realized this was going to make sense in that chapter."
Johnson, who wanted to craft a finale for Luke that "pushes the audience and thus the character," said the decision was blessed by Lucasfilm president Kathleen Kennedy and the Star Wars story group.
But Luke may not have gone the way of Obi-Wan and Yoda just yet, according to Luke actor Mark Hamill.
“Well, I’m still in denial,” Hamill quipped. “I just think he transported somewhere else.”
The Force Awakens director J.J. Abrams will return to a galaxy far, far away for the trilogy's conclusion, in theaters December 2019.
Starring Daisy Ridley, John Boyega, Adam Driver, Oscar Isaac, Andy Serkis, Benicio del Toro, Laura Dern, Carrie Fisher and Mark Hamill, Star Wars: The Last Jedi is now playing.