I was just reading Jabootu’s review of The Island of Dr. Moreau, and it points out that the ostensible hero, named “Edward Predick” in Wells’ book, gets his name changed to “Andrew Braddock” in the 1977 version and “Edward Doughas” in the 1996 version. The reviewrer hadn’t seen the 1932 classic “Island of Lost Souls”, so he didn’t know that in that version he was “Edward Parker”. Looks like no one wants to keep the name fixed. I guess the name “Prendick” amused their inner 13 year olds.
On a related note, Wells’ book War of the Worlds never does name its narrator, so people are free to choose their own name for the protagonist. Orson Welles’ Mercury Theater on the Air, in Howard Koch’s script used the astronomer, named Richard Pierson. The 1953 George Pal movie named his Clayton Forester, but MST3K has pretty much killed that possibility. In 2005 Tom Cruise played Ray Ferrier
Maybe they wanted to avoid paying her estate royalties for using her name in the title? They probably had to do it for the poster anyway, but it would probably have been a lot more for the title.
Not really a simplification, but the movie Road to Perdition changed the character name from the book (and real life gangster) John Looney to John Rooney. They thought Looney would sound too cartoonish for the character in the movie. But that really was his name in real life, though the story is so fictionalized that the name was just about the only real thing left in it.
Trivia: In Japan, the character Sulu was renamed Kato. I’m not sure if there was any reason for this beyond the fact that “Kato” is a Japanese name and “Sulu” is not.