Their homeland was apparently Crete, Greece and the Aegean Islands.
Mass graves are more problematic.
The prolific Greeks spread out over the Mediterranean basin (and apparently around the Black Sea), settling in Sicily and Italy even in Mycenaean times. The Minoans (who were non-Greek, insofar as their written language has been found to be not Greek) were displaced in markets like Caphtor (Cyprus), Israel, and Egypt, as well as the north (and -inthos placenames show up around the Adriatic and Tyrrhenian Seas). Classical Greeks wound up under Persian rule in places where they'd settled like those and in Anatolia. They didn't run into the Sea Peoples, because they were the Sea Peoples.