I just read a memoir by the Chinese short story writer and novelist Yu Hua. In the first three years of his career, he wrote stories were full of graphic violence and death. He also had constant nightmares in which he was hunted down and killed. After one such nightmare, he started thinking about the executions he witnessed during the Cultural Revolution as a child. He grew up in a fairly sleepy town, so the "trials" that were a regular occurrence during the Cultural Revolution were a can't-miss public spectacle. When someone was sentenced to death and taken away in a truck to be executed, he and his friends would race to the execution site, hoping to get there in time to see it happen. If they made it in time, they saw the accused executed with a rifle bullet to the back of the head, sometimes watching from just a few feet away. After the nightmares brought these memories back, he decided that if he wanted to stop this violence from being reproduced every night in his nightmares, he needed to stop reproducing the violence every day in his writing. So he stopped writing about violence, and his nightmares went away.

If you only knew that he grew up in the Cultural Revolution, wrote incessantly about violence for several years, and then stopped, you could easily say that there was nothing strange about that, it's not a head-scratcher, but hearing the story as he tells it is much more interesting than simply saying "it's not strange." Raising this question about Vonnegut, even if it has been raised before, might eventually unearth some information that fleshes out his story.