Star Wars: A New Hope introduced the world to a galaxy far, far away and to the main characters of the Star Wars universe, among those Obi-Wan Kenobi, who didn’t stick around for long as he was killed by Darth Vader – but why did he let his former apprentice kill him? The history of the Star Wars saga is divided into three trilogies, each one covering different events and points in time, but all of them with the Skywalkers at the core of the stories. The films also introduced the most important people in the lives of Anakin, Luke, and Leia, such as Obi-Wan Kenobi.
Played by Alex Guinness in the original trilogy (and Ewan McGregor in the prequels), Obi-Wan Kenobi was a Jedi master who mentored Ben Kenobi. After playing a recording of Leia explaining where the plans for the Death Star were and asking for help, Obi-Wan revealed his true identity to Luke and invited him to train as a Jedi. They carried on with the mission of helping Leia, and along with Han Solo and Chewbacca, ended up on the Death Star. Once there, Obi-Wan distracted Darth Vader so the rest could get back to the Millennium Falcon and escape.
Force Ghost. Fans have wondered why Obi-Wan all of a sudden decided to give up and let Darth Vader kill him, and the most obvious answer is so Luke and company could escape.
Other reasons – either instead of the aforementioned one or in addition to it – are because Obi-Wan knew Luke would jump in to help him, and he wasn’t ready to go against Darth Vader yet, and/or because Obi-Wan realized that the Sith lord was way more powerful than the last time they fought each other, and he wouldn’t have been able to defeat him. However, there’s a very important part in the final exchange between Obi-Wan and Darth Vader where the latter told his former master that his powers were weak, with Obi-Wan replying that if he stroke him down, he would become more powerful than he could possibly imagine. Obi-Wan would have then let himself die by the hand of Darth Vader so he would become one with the Force and therefore become more powerful while also being able to keep guiding his new apprentice.
Obi-Wan’s death so early in the Star Wars saga was necessary to push Luke’s story forward, and until George Lucas decides to give a definitive reason (or reasons) as to why he let Darth Vader kill him, it’s pretty much open to interpretation: whether it was to buy the rest some time, to prevent Luke from fighting Darth Vader before time, to become a Force Ghost, or something else.