Solo: A Star Wars Story underwent a great deal of changes after director Ron Howard replaced original helmers Phil Lord and Chris Miller, and while the movie ultimately underperformed, the surprise appearance of Darth Maul left a lasting impact with moviegoers.
Whether that's a plot thread Lucasfilm is planning to address remains to be seen, but during an interview with Star Wars Holocron, voice actor Sam Witwer indicated that Maul's original role in the spinoff movie might have been quite a bit different. The Star Wars Rebels and The Clone Wars actor also addressed replacing original Maul voiceover actor Peter Serafinowicz.
"There was stuff that had to happen once I got hired," Witwer explained. "There was a reshoot that had to happen because people like me and [Clone Wars and Rebels creator] Dave Filoni were letting them know there were a lot of details that weren’t consistent."
"I don’t want to say that what [Peter] Serafinowicz was doing was bad," he added, possibly indicating that The Phantom Menace star was originally re-hired as the villain. "It just didn’t sound recognizable as the character from The Phantom Menace nor the character from Clone Wars. It was a totally different thing. They needed people to recognize the voice, so there it is."
Witwer went on to say that, "[There were] a lot of things in this script where he growls, he does this, he does that," but when asked to elaborate on Maul's original role, he would only say that, "In 20 years, when I’m fully an old man and don’t care about anything, I will say things that will blow people’s minds and make national news and stuff. But no, I’m not that stupid yet."
It's possible that the team working on Solo: A Star Wars Story were unaware that Maul became a much calmer, more collected character following the events of The Phantom Menace, hence why reshoots took place to change how the iconic villain was portrayed in the film.