This video explains that most of the major Bronze Age city-states in the eastern Mediterranean collapsed at the same time at around 1,200 BC, mostly due to being sacked by a mysterious horde of “Sea Peoples.”  Only Egypt was able to effectively defend itself from the attacks, but the collapse of the rest of the cities in that region weakened Egypt for the next thousand years due to depriving it of trading partners.  The collapse of the civilizations brought about a “dark ages” that preceded a later period of enlightenment in ancient Greece.  Also explained is how the cities in the region were already in a weaked state before the attacks due to various reasons, such as the resource of tin (that is necessary in the process of creating bronze) being a scarce commodity, the climate was going through a 300 year dry period that decimated crops, and many earthquakes were also happening in that region at the time.