why did last year, the higher the cases of Covid19 ,  the higher the stock market went, why?

The same reason the pandemic made the banks and rich people richer (and poor people poorer).

People were not going into stores and restaurants, were not taking vacations, were not using gasoline, etc. Everyone who still had a job accumulated a pile of cash because they had nothing to spend it on. And then billions of dollars of stimulus money went to people who didn't need it. (Although millions of low-wage workers lost their jobs, the middle and upper classes mostly were able to work from home or adapt their workplaces. Total wages paid in 2020 dipped less than 1%)

Bonds have been paying zero interest for a while. Real estate quickly became overpriced as people fled shared housing. So the only place to invest all that money was the stock market.

I dont think that they are necessarily directly part of each other. March was a dismal month for stocks, so that created a great buying opportunity. Like Ive said before, buyers arent going to let a stock get so low before they start to buy back in. The good vibes from buying so low just kept the good Wall Street spirits going.

When Covid first increased, the stock market plummeted.  When markets realized a new virus isn’t the end of the world, markets rebounded.

Last year marked a time of enormous deregulation and lower taxes allowing companies flourish  even in challenging times.  Now we are transitioning to the opposite.   Covid is decreasing rapidly, but increased taxes, increased regulations and deficit spending will stifle the economy eventually. 

Once Biden was in, the hope and goodwill knew no bound. Not it is being proven. 

think of the amount of money that is set free , never mind stimulus cash, thats  nothing.

Because of fleas.