I've been googling alot and visiting lots of chat rooms just looking for some reason for the big drop.
The closest thing that I can see is that lots of major investors around the world are dumping portions of their income producting investments (especially bonds) because they foresee a huge jump in interest rates around the world within the next year as inflation goes for a nasty run.
This means that income producing investments will fall hard so that their yields keep up with the rising rates.
Holding on will be terrible, but when the smoke has cleared and rates have started to peak, income producing investments with high yields will be a steal.
Cheers,
PW