I contest that. The disappearance of this "surplus" (and if you follow history, you know where such surplus typically went – not the common people) was a blessing for all but the palatial elite.
It took over 10 generations for people to forget the horrors of the Bronze Age, with its "economy surplus", and agree to come together again to form centralized societies. That is no co-incidence. You underestimate human intelligence if you believe "the Sea Peoples came and made a boo boo and everyone had no choice but to go dark for 400 years".