We have been there before, for example: https://en.wikipedia.org/wiki/Railway_Mania https://en.wikipedia.org/wiki/Railway_Mania The companies go bankrupt their

We have been there before, for example: https://en.wikipedia.org/wiki/Railway_Mania https://en.wikipedia.org/wiki/Railway_Mania The companies go bankrupt their stuff is sold for pennies & investors loose their money. The now super cheap stuff might get reused for something else, that is actually profitable. Or will just get dumped, like many unprofitable or never finished lines from the railway mania days.