Maudlin sentimentality about doomed young boys and their aged mothers was to the pop music of the 1860s what rage and craziness are today. People couldn't get enough.

The war itself had something to do with this, but much American popular culture was incredibly mawkish throughout most of the century.

Part of the reason was a belief that being made to weep for   imaginary characters was good for you. It led to a greater concern for others, and there were spiritual benefits too: the vivid awareness of piteous mortality turned people toward God.