Different people

Opinion: Robert Shiller explains the pandemic stock market and why it’s decoupled from the economy

NEW HAVEN, Conn. (Project Syndicate) — The performance of stock markets, especially in the United States, during the coronavirus pandemic seems to defy logic. With cratering demand dragging down investment and employment, what could possibly be keeping share prices afloat?
The more economic fundamentals and market outcomes diverge, the deeper the mystery becomes, until one considers possible explanations based on crowd psychology, the virality of ideas, and the dynamics of narrative epidemics.

Schiller's theory of covid psychology requires the same people, but different people occupy the market at different times.

The folks who caused the initial decline were exporters into the USA facing a sudden stop and needed cash. Then came the seigniorage tax and domestic savers enter the market to avoid the tax.

Schiller only works with the average, he needs to consider variance and skew and his analysis would be more complete.