The only reason we're talking about her life at all is because of her remarkable creative vision. If she had taken crappy photographs she would have remained as unknown in death as she was in life.
Right! and Wrong! - vivian Maier had great talent but as Rob C said:
the western world was already drowning in photographic images
And I would add to that "we are drowning in some damn fine photographic images". The problem now seems to be one of quantity. There are billions of images being produced and if only 1/1,000,000th are worth looking at, that's probably thousands more than even 20 years ago before the digital revolution.
So given the huge volumes of excellent images from talented photographers, it makes sense that there needs to be other criteria upon which to base the "saleability" of a photographer's work. So the photographer's life becomes part of the equation. After all, while great art sells, you can sell even more if there's a story behind it and that's what the gallery game is all about - sales.