The Mother of All, The Black Swan

A “Black Swan” event might be followed by the simple expression, “I never saw it coming.” 

What is it, Black Swan (event)?  From Wikipedia:

The black swan theory or theory of black swan events is a metaphor that describes an event that comes as a surprise, has a major effect, and is often inappropriately rationalized after the fact with the benefit of hindsight.

This is far bigger the post-game analysis of the less-than-capable Monday Morning Quarterback; it is a crisis of huge proportions, often irrecoverable, such as: 

1. Climatic Environmental 
2. Thermonuclear 
3. Pandemic
4. International, global economic...
5. Astronomical

As to the economic kind, the following from Investopedia: 

The idea of a black swan event was pioneered by the financial professional turned writer Nassim Nicholas Taleb after the results of the 2008 financial crisis. Taleb argued that black swan events are impossible to predict yet have catastrophic ramifications. Therefore, it is important for people to always assume a black swan event is a possibility, whatever it may be, and to plan accordingly.

 https://www.investopedia.com/terms/b/blackswan.asp#ixzz50PTcSn5b