In a mathematical sense, the relationship isn't as much between the absolute level of the economy and prices, it is the tendency of the economy and the prices. You should look at the first (maybe second?) differentials.
Furthermore, values like GDP are inherently lagging. They show data that has happened months ago. There's almost no new information content in that number. Yes the number is bad, but everyone knew it's going to be bad. It sounds like (judging by the market action) that it wasn't worse than consensus.
Now, all the above is viewed through a lens of efficient markets. Reality is again more complex. As it has been pointed out, the price is not just driven by expectations about the economy or stocks, it is very much driven by central bank and government action. Easy money distorts prices. When Tesla which makes a puny 400k cars a year and has just about stopped being loss making is priced higher than VW which makes >6 million cars a year and made $17 billion, something is off. Let's put that into context, Tesla shares have priced in decades of non-stop geometric (20% YoY) sales growth to justify the _present_day_ valuation.
Don't think for a moment that traders don't know this. It's absolutely a game of musical chairs and they know it. Everyone, and I repeat, even the most boring, backwater pension fund board knows that this is a bubble. Everyone is participating and hopes that when the music stops, they'll have already made some safe haven stockpile to weather the storm.
The downside for those companies will be the regulators at DOJ. I have no doubt they will survive this pandemic in even better shape than before. The question then is if the government will work to break them up.
Obvious examples would be splitting YouTube from Google, splitting Instagram and WhatsApp from Facebook and forcing Amazon to pick a side (own the marketplace or be a seller).
I would also add a #4 to your list that people often miss. There is risk and there is uncertainty (think unknown unknowns). The market hates uncertainty because it is so hard to price. Risk though can be priced. This is often why the market will go up with numbers that look really bad when they come in. They are no longer uncertain.