the dorians and the sea peoples were probably one and the same, and the confederacy probably sailed down from the black sea rather than from sardinia, which is probably a false cognate. that the philistines were of greek origin is apparently told in their own histories, and that ought to be enough to more or less put the origin of the sea peoples to rest, even if it doesn't answer the question as to what exactly caused the collapse - which was probably a combination of factors, partially stemming from climate as a root cause.
but, i just again want to try to present the perspective of the poor, and by that i do not mean the urban poor within the empire. the really poor people were of course the barbarians, and that is true throughout history.
the historian gets it's information from the literate, settled culture of which it is a part of. that is always true, nearly by definition. so, it sees history from the perspective of the city and naturally sees the city as a crowning achievement of human civilization.
but, to the person outside the city - the subsistence farmer or the hunter-gatherer - the city is a source of oppression. it is from the city that the slave raiders come, to steal the children and the wives. it is the city that comes to rape and steal and plunder. so, the city becomes a force of evil, one that must be destroyed.
while it seems that the discovery of cheap iron played a major role in the bronze age collapse, i've long believed that the sea peoples were driven more by revenge than by climate. we see this with the viking raids, which were at one point seen as incomprehensible to history, but are now understood as a self-defence mechanism against the expanding colonialism of the christian church, to the north.
so, might the dorians and their allies have decided to put an end to the slave raiding, to the theft of their children, once and for all - and burned the cities down in an act of vengeance and retributive justice?
we'll never really know.