Why was a small bundle of powdered sugar so important to Kashiram that he fought robbers over it?

The bundle was important to Kashiram due to the spiritual act it represented, not for any monetary value. The source material in Chapter 0 explains that while robbers believed the bundle contained treasure, it was just powdered sugar. Kashiram was carrying this sugar because a saint named Janakidas Baba had advised him to perform the service of feeding ants. Because this pious task was very dear to him, he was determined not to let the bundle go. As Chapter 0 clarifies, his decision to fight the robbers was a defense of this spiritual practice and the instruction he had received, rather than an effort to protect material wealth.