Mostly people panicking.
And people getting money out of stock funds, so banks etc have to sell off too. And then some other shit going on sending it down the pan.
Hold on on what you got, If you like big risks sell off some shit when it has "one" better day. Then buy again later. Shit with this is, you never know if it has one better day it will be it's way up or not, so this might bite you.
Normal people just need to hang on and sweat this one out.
Idiots that kept all their stock after april and the summer deserve what's coming, they should have made their money and reduced their amount of shares when everything was that high.