In the wake of Lucasfilm’s sale to Disney in 2012, a decision was made about the creative future of the “Star Wars” universe. Namely, it was all the previous ‘Expanded Universe’ material like books, comics, games, etc. being rendered void.
It also meant that everything subsequently coming out after that point would be canon and managed by the Lucasfilm Story Group. During a recent interview with Syfy, said story group member Leland Chee offered a more in-depth explanation for the scrapping of the Star Wars expanded universe and how it ties back to Chewbacca:
“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.”
So it was the entire EU was dumped, even as some elements of it have worked their way back into the official canon of the universe – notably the inclusion of General Thrawn as a character on “Star Wars Rebels”.