Considering both were literate societies deep into historical time, most detail about the Etruscans and the Carthaginians remain obscure.

How aspects of Halstatt and La Tène culture spread to cover an area stretching from Ireland to the Black Sea (with offshoots planted in Anatolia by Greeks) without conquest is a matter for speculation AFAIK, although I'm no expert.

The "Sea Peoples" who devastated the Levant around 1200BC remain utterly mysterious, although there's no shortage of guesses about them. This is a really big one as they disrupted a quite stable pattern of politics that had persisted in that part of the world for a long time.