For one Lucasfilm employee, the decision to change Star Wars' canonical Expanded Universe to the non-canon Legends may come down to one event, the death of Chewbacca. Since the Star Was brand was acquired by Disney many decisions, both big and small, have angered fans. One of the longest lasting controversies though, surrounds the decision to wipe out all canon outside of the mainline movies, before the release of The Force Awakens.
Although J.J. Abrams' film was the first time that Han, Luke and Leia appeared on the big screen together, it wasn't their first adventure since Return of the Jedi. The main heroes of the original trilogy (and other beloved characters) went on a number of adventures through novels, comics and even video games. All of these stories were considered canon and included aforementioned big events like the death of Chewbacca. With the creation of the new trilogy and other new projects, all of those stories were wiped away. While the erasure of the Expanded Universe does simplify things and help new fans approach the material. In on worker's mind, it wasn't the deciding factor for the change. That factor was the death of Chewbacca, the Millennium Falcon's co-pilot.
In an interview with Syfy's Fandom Files podcast, Lucasfilm employee Leland Chee explained exactly why he thinks the EU was cleared. Chee runs The Holocron, the internal database of all Star Wars knowledge. He's also an integral part of Star Wars Story Group which keeps the various movies, comics and video games in the Star Wars Universe from contradicting each other. According to Chee, the decision to get rid of the Expanded Universe wasn't a given once Disney bought Lucasfilm. However, once it was figured that Chewbacca's death should be reversed, everything else followed.
In the 1999 novel The New Jedi Order: Vector Prime, Chewbacca ends up sacrificing himself for Han Solo and his friends. Chewie, so that Han and everyone else may live, ends up dying when a moon falls on top of him. Chee talked about Chewbacca's death (and its reversal) by explaining:
For me it came down to simply that we had killed Chewbacca in the Legends — a big moon had fallen on him. Part of that [original decision] was Chewbacca, because he can't speak and just speaks in growls, he was a challenging character to write for in novels. Publishing had decided they needed to kill somebody, and it was Chewbacca. ... But if you have the opportunity to bring back Chewbacca into a live-action film, you're not gonna deprive fans that. There's no way that I'd want to do an Episode VII that didn't have Chewbacca in it and have to explain that Chewbacca had a moon fall on his head. And if we were going to overturn a monumental decision like that, everything else was really just minor in comparison.
In Chee's own words, the "resurrection" of Chewbacca was the "death" of the Expanded Universe. Although Chee stressed later on Twitter that that's just his personal justification. The decision to reverse the EU wasn't up to him.
Chewbacca being dead/not dead is merely my personal justification/rationalization for the EU reboot. Nothing more.— Leland Chee (@HolocronKeeper) January 15, 2018
Even if Chee's thinking isn't an official explanation, it does make a whole lot of sense. As beloved as certain parts of the Expanded Universe were, it would be almost impossible to start a new trilogy and try to keep all of those stories canon. It would've been absurd for The Force Awakens to have Chewbacca be absent and explained he died off-screen.
It would've been an equally herculean (and silly) task for Chee and company to go through the Star Wars novels and pick out certain events and characters as canon. If one part of a novel isn't true, that should really mean the whole thing is false.
Of course, Star Wars has found ways to revive in the Expanded Universe in the new canon. Admiral Thrawn, a huge antagonist in the novels, is a part of canon once again being a major character in the TV series Star Wars Rebels. In addition, Kylo Ren is very similar to Jacen Solo, the son of Han and Leia who turned to the Dark Side in the books. Even Rey's journey in the new trilogy seems similar to Luke's story in the Expanded Universe.
The Expanded Universe isn't so much dead. It's more in hibernation. At least, to paraphrase a certain Star Wars phrase, that's the way it seems from a certain point of view.
Source: Syfy Wire