Earlier quoted context omitted.
>What am I getting wrong? You are correct when taking the view of the financial sector as a whole - every asset purchase merely swaps who has the cash and who has the asset. You're not getting much of anything wrong, merely missing a behavioral trait of many market participants: they desire a fixed ratio between their various financial assets. An extreme example of this is an index fund, which has a formulaic relatio…
So let's say that the entire world is index funds (plus the stocks they own). An index fund has "too much cash", so they buy stocks. Some other index fund sees that the price is attractive, and sells, but then that fund has too much cash. But the funds each keep some amount (1%?) of their assets in cash. So isn't the net result that stock prices go up until the value of the stock is 99 times the amount of cash in the…
But it's not the only one. Fear of a price drop can be motivating too.