While a stock price is rising, there is a marginal material incentive to invest in it whether or not it is inherently valuable. Bubble.
When questions are raised about an apparently overvalued stock by external events or the availability of new information, and its price starts to fall, every stock holder has a marginal material incentive to divest from it. Crash.
The efficient markets hypothesis is significantly discredited, and it's clear that investor behaviour is governed by aggregated marginal incentives to participate in delusional market activity. Just look at the crypto bubble.
No doubt markets have their uses relative to the crippled planning systems they have out-competed or displaced, but these structures remain a fairly stupid, and increasingly stupid in the presence of superior alternatives, way of distributing capital to economically productive activity. We are barbarians.
