It's not really possible for the market to drop only a little bit in response to half the economy shutting down. Stock prices are an expectation of future cash flows, so they have to drop on news that a huge chunk of those future cash flows are cancelled.

Look at Boeing stock.

Companies dropping 50% because they miss 3 months of revenue?

If that 3 months risks a bankruptcy, that might be right. Long-run valuation for shareholders doesn’t matter if the bond-holders end up with the company.

I suspect this is a 12-24 month economic event, maybe longer before it fully rolls through.

It’s insane to think that Boeing will just return to normal in 3 months. This could depress air travel for years.

You're right about the financials but wrong about the direct economic impact. It's a 3 month hit that people are accepting, with the underlying fear that it will be a year-long hit, and the sickening feeling that recovery from this will take at least 5 years.