Why do equity markets react so strongly to good news?

During the COVID crisis and since the beginning of the war in Ukraine, equity markets have reacted very positively to any good news. Why is there such an optimistic bias among equity investors? Probably because: Holding cash or bonds generates an extremely negative real return; Companies' financial situation improved rapidly in the aftermath of the COVID crisis; Investors do not expect a sharp rise in interest rates that would make bonds attractive again and cause share prices to fall; In an environment of negative real interest rates, holding equities protects against inflation.