Andre Kertez, W. Gene Smith? I do not know for sure. I would think a photojournalist.
As for Grandma Moses compared to O'Keefe, they are both very different in their styles and subject matter. Moses' fame apparently seems to be more of an accident. Her fame was due to a chance finding by Louis J. Caldor, yet he recognized her talent. As compared to O'Keefe, who benefited more from that marriage, Steiglitz and her? O'Keefe was far more celebrated during her lifetime. Grandma Moses received fame for the last 25 years of hers. Chances are she would have remained in obscurity if not for that chance discovery of her paintings in a remote drug store.
Van Gogh, yes he starved, lead a tormented life, institutionalized for a time, was supported by his brother which Vincent resented. Actually he originally studied to be a minister and was very zealous before turning to painting. Mozart buried in a paupers grave, supposedly murdered by his arch rival Solieri who was very jealous of Mozart. Solieri was the court composer to the king yet history shows his work was mediocre at best and he may have deliberately oppressed Mozart's work out of sheer jealousy.
The one common denominator between most artists is that they receive little or no recognition during their lifetimes. Only the lucky few enjoy fame during their lifetime. Others get it postmortem, some taking years before a champion comes along to promote his work, most never. Just because one artist's work is promoted over another, does not mean it is warranted. What the galleries promote is often more of trying to follow or promote popular trends so they can make a living. Monetary success is not always the deciding factor. Is Thomas Kinkade a great artist or a great marketer, salesman? Picasso certainly was great and wealthy during his lifetime.