I also struggle with this, and this is my theory:
In 2008 every day brought in bad news, with more and more banks failing, home being foreclosed, bad financial numbers, Congress trying to bailout .... which led to overall bad sentiment and the decline in stock market.
Right now, if I look at the new cycle what do I see: A city wants to open up, layoffs, a state wants to open up, stimulus money, people on the beach, layoffs, more stimulus money, GDP down, virus in works, 20% in NY may have been infected, Remdesivir is working....
So, is it a bad news or optimistic news? It's all mixed in. No one knows how to process medical side and financial side together. On top of that there is a lot of liquidity in the market. So, what happens, it ends up in the stock market thus inflating it.
I think there would be a massive whiplash once we start seeing higher unemployment numbers and the real impact of March-? shutdown and see a massive drop in the stock market.
But who knows??