You're absolutely correct. However what is different is that the upside of the boom (above what it should be) is so high that the correction is at least almost as big a downside. There are two ways that the market correction can occur, a sharp correction would cause many problems, a slow recession would ease the pain somewhat but would take too long.

The actions you're seeing in the US, UK, EU and Japan are all designed to lessen the steepness of the drop.