Other people call Bitcoin a "Pyramid bubble"


Wikipedia
A Ponzi scheme is a fraudulent investment operation that pays returns to its investors from existing capital or new capital paid by new investors, rather than from profit earned by the individual or organization running the operation. Operators of Ponzi schemes usually entice new investors by offering higher returns than other investments, in the form of short-term returns that are either abnormally high or unusually consistent. The perpetuation of the high returns requires an ever-increasing flow of money from new investors to sustain the scheme.[1]

When a Ponzi scheme is not stopped by the authorities, it sooner or later falls apart for one of the following reasons:[1]
The promoter vanishes.

Satoshi Nakamoto vanished