As explained many times here, it’s the machines squeezing out the broad market index put buyers and short sellers.
It’s that simple.
The gamblers are addicted and won’t stop until they are broke.
Of course this does not make for good ‘doom porn’ or justify the geniuses that work on Wall Street; so, you won’t hear this story in the mainstream much. (some others have pointed this out recently too – but it falls on deaf ears).
Cheers