They can fall 90% slowly. Look at south Europe after 2018

I did, and did not see a 90% fall.

The Greek stock exchange went gradually from ~5,500 in 2007 to ~ 500 in 2011.

The recovery started only after 2020 ish. Today it is around ~1,500.

Edit: Oh now I see. I had a typo. I meant to say the crash happened after 2008 not 2018.

Stocks overall? No.

The few stocks I might have specifically invested in? Possible.

Then it'll be a good lesson for you to diversify investments.

You're totally missing the point, but ok.

What was the point?

When faced with "cash in hand that might lose value through inflation" versus "the stocks you currently own at risk of being worthless", the decision to sell is straightforward even in the absense of a next step.

There is always a risk that a specific stock will go to 0. It happens even in good ecconomic times.

The decision to sell is not straightforward, even given the current situation. It would probably be the wrong decision for the average person unless you really know what you are doing.

Under ordinary circumstances, sure.

But right now, sell sell sell is a forgiveable reaction.