In the USA, my nomination for one of the worst examples of malinvestments is the 2008, and now the COVID-19 induced, “investments (bailouts)” of the supposed to-big-to-fail Wall Street banks. Billions of dollars were, and are now, being “loaned” or given to Goldman Sachs, AIG, Bank of America and others to shore up their foundations which are crumbling due to their poor monetary decisions over the course of many years.
https://projects.propublica.org/bailout/list
My argument, in general, is if banks are so irresponsible that they don’t plan for economic crisis properly and they become insolvent, let them fail. Despite the massive pain this would initially cause in public and citizens lives, it would serve as a good example to other institutions that the government will not always be there to hold their hand and catch the when they fall. My hypothesis is that the others remaining would take note and adjust their practices accordingly.