A glance at elite marriages show rich, famous and powerful men marrying women that are young enough to be their grand daughters. Sometimes these men are known bad boys. What does this have to do with civ collapse? Debt? Over population? Competition for resources? Food shortages? And generally spending more than you earn?
following joseph tainter, vaclav smil, ronald wright, jared diamond, peter turchin and niko tinbergen Failure is the best option