From Wikipedia

Aegean Collapse

How the Bronze Age ended in this region is still being studied. There is evidence that Mycenaean administration of the regional trade empire followed the decline of Minoan primacy, and that several Minoan client states lost much of their population to famine and/or pestilence. This would indicate that the trade network may have failed, preventing the trade that would previously have relieved such famines and prevented illness caused by malnutrition. It is also known that in this era the breadbasket of the Minoan empire, the area north of the Black Sea, also suddenly lost much of its population, and thus probably some cultivation.

Recent research has discredited the theory that exhaustion of the Cyprus forests caused the end of the bronze trade. These forests are known to have existed into later times, and experiments have shown that charcoal production on the scale necessary for the bronze production of the late Bronze Age would have exhausted them in less than fifty years.

One theory says that as iron tools became more common, the main justification for the tin trade ended, and that trade network ceased to function as it once did. The colonies of the Minoan empire then suffered drought, famine, war, or some combination of those three, and had no access to the distant resources of an empire by which they could easily recover.

Another family of theories looks to Knossos itself. The Thera eruption occurred at this time, 110 kilometers (70 mi) north of Crete. Some authorities speculate that a tsunami from Thera (more commonly known today as Santorini) destroyed Cretan cities. Others say that perhaps a tsunami destroyed the Cretan navy in its home harbour, which then lost crucial naval battles; so that in the LMIB/LMII event (c. 1450 BCE) the cities of Crete burned and the Mycenaean civilization took over Knossos. If the eruption occurred in the late 17th century BCE (as most chronologists now think) then its immediate effects belong to the Middle Bronze to Late Bronze Age transition, and not to the end of the Late Bronze Age; but it could have triggered the instability that led to the collapse first of Knossos and then of Bronze Age society overall. One such theory looks to the role of Cretan expertise in administering the empire, post-Thera. If this expertise was concentrated in Crete, then the Mycenaeans may have made political and commercial mistakes in administering the Cretan empire.

More recent archaeological findings, including some on the island of Thera, suggest that the center of Minoan Civilization at the time of the eruption was actually on Thera rather than on Crete. According to this theory, the catastrophic loss of the political, administrative and economic center by the eruption as well as the damage wrought by the tsunami to the coastal towns and villages of Crete precipitated the decline of the Minoans. A weakened political entity with a reduced economic and military capability and fabled riches would have then been more vulnerable to human predators. Indeed, the Santorini Eruption is usually dated to c. 1630 BCE, while the Mycenaean Greeks first enter the historical record a few decades later, c. 1600 BCE. Thus, the later Mycenaean assaults on Crete (c.1450 BC) and Troy (c.1250 BCE) are revealed as mere continuations of the steady encroachments of the Greeks upon the weakened Minoan world.

Each of these theories is persuasive, and aspects of all of them may have some validity in describing the end of the Bronze Age in this region.