This was part of what’s now known as the bronze age collapse about 1200 bc.
three causes have been identified.
1.)drought
2.)earthquakes
3.)invasions of the sea peoples. These were from various tribes around the medeterranian including the cretes and greeks and phoencians. Its now thought that that the impetus group and largest among them were from the Po valley in northern Italy.
Here’s a good book on the subject.