But the explanation is that is was destroyed by fire during wars.
Btw, I have read somewhere about a submarine volcano, west of Portugal, Mt.Tores something, causing this flood/tsunami.
During the period of 2600 B.C. to 2400 B.C. there were signs of stress beginning to appear in the Millaren culture. Their fortifications were reinforced and enlarged to their maximum extent indicating violent encounters or war with the neighboring peoples from the west and north of them. It was in this period that the first Maritime Bell Beaker pottery appeared among the Millarens. The pottery spread quickly throughout the region on the existing maritime trade networks. By 2400 B.C. the social stress facing the Millarens began to worsen into a crisis and the large settlements began to depopulate. The graves of the elites were increasingly accompanied with weapons indicating the violent nature of the time. By 2200 B.C. the town of Los Millares was abandoned after a sequence of catastrophes (probably large-scale warfare). There is evidence of widespread fires and damage to the fortifications. But amid the destruction, the first settlements of the El Argar arose to take their place. The period began with the use of bronze in the Aegean in 2600 B.C. and ended in 2200 B.C. with it being used by the Beaker people in Britain.
And the submarine volcano is the "Torre Seamount".