For the first time I can remember, uncertainty is a valid excuse. Historically, uncertainty or lack of visibility has been used to cover up problems. This time around, no one knows with any degree of certainty what will happen.
The perfect storm, or double whammy, of coronavirus and the oil-price spat between Saudi Arabia and Russia gave the excuses to the stock market to correct, after an unprecedented 11-year run. The speed of the 30% or so fall in stock markets is the defining difference compared with previous falls in 2008, or after 9/11, or during the dotcom bust or recession of 1991/92, along with the infinite uncertainty. There is no comparison really with any previous recession — this is only like wartime.