The point being, these "strong companies" you speak about are what make up the index funds, so if they have internal issues, it translates to the indexes.
The other point, the majority of people are clueless to search and learn about company internals, or just don't have access to these particular companies, and only have the limited index funds in their 401Ks to invest in. So, for many, they're just stuck on the roller coaster for the ride.
There's been a bunch of major corporations the past week, that have posted that their business will take a economic hit from this panic, due to slow downs. I expect a whole bunch more in the near future to do so. Strong company or not, they need the sales to keep the balls in the air. And, with record high corporate debt levels, it wouldn't take much for them to start hurting.
Unfortunately, the majority of businesses can't afford to sit on their "economic hands" for 4 months, waiting for the panic and hype to calm down.
This is a good time for trump to convince factory manufactures to invest in the homeland. rebuild our economy even further make America self proficient. At a time like this it is best to be an optimist rather than a pessimist. The Dems will create havoc and do their best to destroy our economy right now it is their only chance at winning back. And don't think for a second this virus was not man made gives me second thoughts about the whole thing and who better to destroy an economy so reliant on another country.