Why do bubbles collapse at all? When valuation changes cause widespread insolvency, imo. That was possible in 2008 because household debt levels combined with

Why do bubbles collapse at all? When valuation changes cause widespread insolvency, imo. That was possible in 2008 because household debt levels combined with the subprime scams create underwater households that could no longer keep up with payments. Who would become insolvent when tech stock valuations change?