Many believe the economy has been propped up by the Fed (by lowering interest rates) because they've been afraid of a recession. The Fed also doesn't really have any more ammo left to prop things up.
So, the cause is that the Fed has been propping an economy that is ripe for a recession and a reset. The coronavirus is the trigger that will force the hand.
Many currencies have been propped up and artificially kept competitive via QE as the new tool to augment interest rates as having driven them so low, they had to use something else. The next tool in the box is negative interest rates.
Kinda all leads into a perfect storm, and now have whole generations having grown up with no saving mentality and a have today, pay tomorrow expectation that if things ever go back to normal, real interest rates that encourage responsible spending instead of artificially stimulating an economy. Well, it will be a huge education for many and as always, the people end up paying for it.
So, the cause is that the Fed has been propping an economy that is ripe for a recession and a reset. The coronavirus is the trigger that will force the hand.