That's not what the "market thinks" at all. The stock market is much more complicated than you assume it is. But if you want a really simple explication: 4t$ more in circulation chasing the same amount assets, interest rates make it non viable to hold bonds, and you don't want to buy bonds anyways if you expect a more inflationary economy. If there's expectations of inflation, you go for stocks and if there's inflation AND 0 interest rate, you RUN for stocks.
You can also think of it this way, retail investors can afford staying in cash indefinitely but make up a tiny portion of the capital. Big money NEEDS to either buy bonds or park their capital in any yielding asset. Right now treasuries offer safety but negative real yields for probably a long time. But a pension fund still needs to generate returns to pay it's beneficiaries. So what's the best and cheapest option right now, by far? Stocks. You have to keep in mind that prices are relative so if stocks are relatively cheaper than bonds you buy stocks. Now add 4t$ to that and you get a stock market that stays strong even if everyone in the market knows the huge economic risks we are facing right now.
Never assume that a whole entire sector that has so much incentives to price in all the available data would just ignore something because they feel like it. I don't get how people really believe that.