G.I. Joe: Retaliation killing off Channing Tatum's Duke was a bold choice, but here's why the studio probably regretted it. Director Stephen Sommers scored a major hit when he directed 1999's The Mummy. This remake of the Universal horror classic had spent years in development hell during the 1990s, where filmmakers from George A. Romero to Clive Barker tried to crack it. Sommer's suggestion to basically make it an Indiana Jones movie is what got the project a greenlight.
Sommers was quite busy in the years that followed, directing The Mummy Returns and Hugh Jackman's Van Helsing in addition to producing other projects. His last major blockbuster was 2009's G.I. Joe: The Rise Of Cobra, which starred Channing Tatum, Sienna Miller, and Joseph Gordon-Levitt. The movie was a modest success but received mostly mixed reviews, though some reviewers enjoyed its cartoonish tone. Paramount decided to soft reboot for sequel G.I. Joe: Retaliation, which introduced Dwayne Johnson as fan-favorite Roadblock and new cast members like Adrianne Palicki and Bruce Willis. The sequel only featured a small number of returning characters from The Rise Of Cobra too and a (slightly) more grounded approach to its action
G.I. Joe: Retaliation proved to be a bigger hit than the original, but while there were plans for a third movie focusing on Roadblock, it has yet to arrive. A spinoff dubbed Snake Eyes is due for release in 2020. One of the bolder moves of the sequel is the death of Channing Tatum's Duke, who was the lead in the original G.I. Joe. The character is killed in an airstrike early on which only leaves three survivors, including Roadblock, who then seek revenge on Cobra.
Duke's death was more or less spoiled during trailers for G.I. Joe: Retaliation, where it's stated only three survived and Duke clearly isn't among them. That said, it works in the movie itself as Tatum was prominently featured in promotional material and shares good chemistry with Dwayne Johnson. Killing off the main character of the previous entry was also the sequel's way of stating it was starting from scratch. While it might have seemed like a good idea at the time, it's likely the studio came to regret it.
G.I. Joe: Retaliation was released just as Channing Tatum was becoming a major star, thanks to movies like 21 Jump Street and Magic Mike. There were even reports the studio ordered reshoots to make Duke a bigger part of the story, though this was never confirmed. While having Duke die works for shock value, G.I. Joe: Retaliation takes time to establish the buddy dynamic between him and Roadblock, only to kill the character and essentially replace him with D. J. Cotrona's bland Flint. Tatum and Johnson's dynamic would have worked far better, though its likely Tatum himself just wanted out of the series. He admitted in a 2015 Howard Stern interview to "hating" G.I. Joe: The Rise Of Cobra and only made it out of contractual obligation, so Duke's early exit was probably something he encouraged.