Final answer:
The civilization that disappeared around 300 BCE left behind almost no written records. The reasons for its disappearance could include a combination of climate change, environmental disasters, warfare, and epidemic diseases, which remains a point of debate among historians.
Step-by-step explanation:
The civilization in question, which disappeared around 300 BCE, left behind almost no written records, and the reason for its disappearance may be attributable to several factors, including climate change. This lack of records makes it difficult for historians and archaeologists to ascertain a definitive cause for the collapse. However, based on various archaeological findings and historical records from surrounding civilizations like the Mycenaeans, the Indus valley, and the Classical Maya, a combination of environmental disasters such as droughts, warfare, internal strife, and perhaps epidemic diseases could have played significant roles in the decline of these civilizations. These factors may have led to population decline, economic downturn, and the eventual abandonment of cities, signaling an end to the thriving culture that once was.