Basically, the Japanese bubble economy of the late 1980ies was exactly the same thing as the boom in the USA prior to the Great Depression
in 1929, or the 1999 .com boom
It seems that in the case of the bubble economy the de rigeur thing to blow money on and bait investors with was tourist attractions that were flashy and impressive, but too expensive in maintenance, and with far fewer actual visitors than planned.
Stock prices skyrocketed not because of an actual increase in productivity, but because people knew they would rise, and they knew that because everbody was buying like crazy. Eventually, it became simply too ridiculous to keep believing in, and the bubble burst. Many people lost their livelihood, and the country still hasn't completely recovered.
The sad thing is, things like this will most likely happen again (it already did at least once), and again as long as the stock market keeps working the way it does (i.e. psychology often counts more than solid facts).