How did the Last Supper crack?

The Last Supper, painted by Leonardo da vinci, began to deteriorate soon after its completion due to the experimental technique he used. Instead of traditional fresco, da Vinci applied tempera on dry plaster, which made the mural susceptible to moisture and environmental factors. Over the years, the painting suffered from damage due to humidity, pollution, and even the building's use as a barracks and a stable. Restoration efforts have aimed to preserve the artwork, but the original details have been significantly lost.