It could just be irrational exuberance, and the perverse incentive to keep it going by the people running those companies.

In the dotcom bubble I’m sure there was shortages, same as the housing bubble which destroyed peoples ability to buy a home.

Its really the Fed whose at fault, with cheap debt and QE, they now exist to create as much misallocated capital as possible. The entire financial system is fraudulent, to quote burry in the big short.