If you could predict the future with certainty, we would not all...

If you could predict the future with certainty, we would not all be rich.
Excepting dividends payment or other corporate actions. It is zero sum game. If I get richer, it is because someone else get poorer in cash terms.

The stock of RMD goes from $21 to $23 is because traders/investors put more money/cash to bid up the price. If some traders/investors decide to get out of the position and the number of traders/investors reaches a certain threshold, then the price of RMD goes back to $21 or lower.

The fact is that the price of RMD holds up or goes up is because we put money into RMD stock. The first batch of traders/investors who withdraw money from RMD makes money from the rest of traders/investors who withdraw money from RMD later. If majority of traders/investors decided to withdraw money from RMD, last cohort of RMD shareholders hold the bag lost most their money.

In the meantime, if we all decide to hold the stock not to sell, we can be all paper rich, not cash rich in general. This means that, the paper rich RMD shareholders withdrew money from the RMD stock, RMD shareholders become poorer while traders/investors continue to withdraw money from RMD/sell RMD.

Basically, it is zero sum game, aside from dividends payment or other corporate actions.
Food for thoughts, maybe It does not make sense to you.