the book
The book won the first Newbery Medal and was written for young adults to explain the situation in the world in 1921. Apparently on all entries he asked himself, "Did the person or event in question perform an act without which the entire history of civilization would have been different?" It seems that the movie took the title and not much else from the book, which wasn't unknown to happen with Hollywood adaptations. I haven't read it so I can't say if it's as idiotic as the movie but it's hard to believe a book could be and sell more than one copy let alone have gotten any other award than the booby prize.
Wikipedia says, "He was born in Rotterdam, the son of Hendrik Willem van Loon and Elisabeth Johanna Hanken. He went to the United States in 1902 to study at Cornell University, receiving his degree in 1905. He was a correspondent during the Russian Revolution of 1905 and in Belgium in 1914 at the start of World War I. He later became a professor of history at Cornell University (1915–17) and in 1919 became an American citizen." Doesn't sound as if he wouldn't know an historical fact if it bit him. I'm guessing that would apply to the Hollywood scriptwriters, though.