The price of securities is also an interface between the perceived value of the company and the value of US dollars exchanged for shares thereof. So while the market may be “bullish,” it could also be that the value of dollars has dropped and it takes more of them to convince another trader to let go of their shares.
Obviously the forces at play are quite complicated, but it’s my belief that this is driving a good part of the rise. Who wants cash when the Fed is printing $trillions? Companies can raise their prices to keep their costs at the same fraction of revenue, so in the current environment of loose money it seems a sounder investment to many, especially if the government eventually continues the direct-to-citizen stimulus.
This is not financial advice etc.