Final answer:
During the Holocaust, most of the world knew nothing about the murder of the shadow children at the rally due to survivors' hesitancy to talk about their experiences and the lack of awareness among non-Jews about the extent of the genocide.
Step-by-step explanation:
During the Holocaust, most of the world knew nothing about the murder of the shadow children at the rally due to various reasons. Firstly, many survivors were hesitant to talk about their experiences, and the focus in Israel and elsewhere was on acts of resistance rather than the victims. Additionally, non-Jews were often unaware of the extent and organized nature of the genocide. It took decades for the full scope of the Holocaust to be recognized and understood.