(You flipped the page.)
After minerals were discovered in Steam Mine Mountain, people began to carry out mining operations without first conducting a survey of the terrain.
Thus, humans did not see the camouflaged Hard Skinned Cloned Beast in the area and accidentally injured them while digging. The beasts saw this as an attack and began to defend themselves violently.
After years of evolution, the Hard Skinned Cloned Beasts possess an acute sense of alert. They carry out defensive attacks whenever other creatures approach them.