A lot of historians credit one of the major Reasons for The Fall of the Bronze Age as the "sea people" being one of its main causes.

The "Sea Peoples" were dispossessed victims of the disturbances at the end of the Late Bronze Age, not a root cause. Note that several of the groups are attested more than 200 years before the end of the Bronze Age, often allied with the major powers like the Egyptians and Hittites. In the Battle of Kadesh (ca. 1280 BCE), for instance, the Sherden fought on behalf of the Egyptians, and the Lukka fought on behalf of the Hittites. They were also often hired as mercenaries by the smaller city-states in the Levant. For example, in two letters to the king of Egypt (EA 122 and 123) dating to around 1340 BCE, the vassal king of Byblos complained that the Egyptian governor of nearby Kumidi killed a Sherden within his town (presumably a mercenary hired by Byblos), and the outraged people of Byblos demanded justice.

Paḫuru perpetrated a great misdeed against me. He sent Sutean men, and they killed a Sherden and took three men (as captives) into the land of Egypt. And for how many days has the city been enraged at me! And behold, the city is saying, “A deed that has never been done since time immemorial has been done to us!” So send the men (back to Byblos) lest the city commit rebellion.

There's always more to be said on the Sea Peoples, but I've written about them in a few past posts:

• What do we know about the so-called Sea People's origins?

• Tell me about the Philistines vs others in the Levant 1200 to 800 BCE

• Karatepe and Çineköy inscriptions: Luwian and Phoenician and Sea Peoples