Well, they turned on the money spigot at the Treasury and flooded the marketplace with cash, made all the less expensive by pressing Greenspan to lower interest rates when the situation did not call for it. Kept the market booming, albeit artificially, for a number of years. We still have not paid the 'hangover' price that has to work itself out through the economy. But if you want to see the impact on another once powerful economy that implemented the same policies, check out Japan.
Not only did they turn on the money spigot, Greenspan never increased margin requirements to buy stocks on margin during the bubble. If you recall, all the major brokerage houses did his job for him by restricting the margin puchase of a lot of the dot-com stocks. If I was Greenspan, I would have been embarassed about that lack of proper regulatory action.