It makes sense for this type of art movement to be created. During the time it was created, World War I was going on. It was not a good time. World War I marked a change in warfare permanently with the new machine gun technology. Wars were more brutal and frightening, not that they weren't frightening before. So, I am not surprised Expressionism came out of this. Death and human disasters seem be a major part of World War I and Expressionism is the art that came out of it.
If war never occurred, I think Expressionism would exist because there is still death and disasters. Although it would be a little different because it would be displaying different forms of human struggles. Ultimately, Expressionism expresses human struggles and pain. Whether war caused it or not, it would exist because there is still death and disasters.