If the Fed sees imbalances, it can raise short-term rates to quell those imbalances. If it has to, it can take short-term rates to the point where it can cool off not only the imbalances but the whole economy. Again, you have to suspend the notion that the Fed is not that powerful. And you have to accept the notion that short rates matter. When people buy things, they often buy them on credit.
Businesses buy things on short-term credit.
If the price of that short-term credit goes up too much, it becomes prohibitive to stockpile inventory. If you can't stockpile inventory, whether it be cars or stocks, you can't exploit the imbalance to your own favor. It becomes too expensive. Psychologically, also, people who run big money in this country are acutely aware of the power of the Fed. They are aware because they look at history.