Why?

If you read Ansel's books, you'll know that he was a master in the darkroom. He was a master in the darkroom because the process of printing from the glass negatives required dealing with precisely one million different kinds of annoying bullshit, due to limitations in film and chemistry. He had to become great at dodging and burning and farting about with chemicals, because if he didn't, his prints would be ass.

I have seen this picture - The Tetons and The Snake River - many times, and I have spent a long time considering it. What makes it great? The composition. The use of light. The sense of distance and scale. The encapsulation of the character of a wilderness that is both beautiful and savagely ready to kill you.

There's an artisanal, craftsmanlike element, too: the work done to ensure that the detail in the river is preserved as well as the bright bit in the middle, the masterful use of the zone system to establish the correct exposure, etc. yadda and so on.

But that's like getting interested in the brushes that Leonardo used to paint the Mona Lisa.