They've invested not for any logical reason, but because everyone else was throwing money at the same thing. That's what happens to dot-coms, the Internet Web sites selling goods and services to consumers. Few of them made money, but their stock prices continued to climb on the basis that somehow, sometime in the great bye and bye, they would return huge profits to investors. A lot of this kind of investing behavior has to do with the times. We are in a period of great change.
Productivity is way up.
Because of that, wages are outpacing inflation, while prices are mostly stable. Yet that very technology has pushed our economic system into overdrive. Capitalism always has done well creating wealth. However, it also destroys wealth. We all know the story of the buggy whip manufacturers who saw their factories ruined by the automobile.