Mike,
From what I've recently found, Jacques Futrelle had first risen to fame as a writer of short stories, literally hundreds of them for The Saturday Evening Post and other magazines.
It is very frank of you to admit that you assumed Futrelle was only well known AFTER the Titanic. This is the attitude of so many of us toward all of the better known figures on Titanic. Not that it applies to you, but for a lot of us I think this is because we are so caught up with the story of Titanic and know so little else about that era that we sometimes have a hard time imagining her people outside the context of the disaster.
Futrelle was already an established writer, with a wide readership, albeit a relatively "new" one, but think how relatively "new" Conan-Doyle was in 1912. We think of Conan-Doyle in a larger context because his career was not cut short. Still, Futrelle is included in several notable anthologies of great 20th century writers. I believe some reviews of his work are online and give a good overview of his career. In my own research, I've come across several old films of the silent era (and one I think from early sound) based on his books and stories.
Frank Millet's fame is also often considered a mediocre one or at least one that never reached it's full blossom. This is far from the truth. Millet's reputation was stellar and widely acknowledged. Even if his output was comparitively restrained and intermittent,Millet was still a major figure in the arts of his day. In his case, he'd already led a long life but because he died in such a legendary disaster, that's what people remember best.
So much is made about prominent Americans on Titanic, but really the most famous man aboard was British. Without question William Thomas Stead was a giant in media and political circles, a social activist of wide range, a hugely controversial, outspoken character, a greatly loved yet much criticized public figure, but sadly a man who today is almost totally unremembered, even among Titanic enthusiasts.
The list goes on...
Randy