The virus is a classic trading 101 example of an obvious screaming buy opportunity, due to totally irrelevant news which doesn't affect any of the underlying forces actually driving the bull, but nevertheless causes investors to panic and put stocks on sale.
Quarantining entire cities. Shutting down thousands of daily US international flights to China. Shutting down on hundreds if not thousands of US retail and manufacturing locations in China.
All of these things are negative for corporate earnings, and should drive stock prices lower...
But like you said, "they do not affect the underlying forces actually driving the bull". And what are those forces driving the bull? Hundreds of billions of dollars in liquidity injections by the Fed and PBOC.
Is this prosperity real? No. But we will all play along as if it is.