1) US government pumps massive amounts of money into the system to prop up asset prices and get themselves reelected. Sometimes called the Fed put.
2) Investors bid up asset prices because they think there is little downside. Sometimes called momentum trading.
3) Doomsters write books and buy gold, pointing out this can not last, forever.
4) Smart money accesses the amount of risk they can handle and then develops an investment portfolio. Classic mix is a lot of real estate and stocks, along with a little cash and gold.
5) World comes to an end. Nuclear annihilation is not popular anymore, but epidemics are on the increase.
The doomsters are right, but the hard part is when?