Computer driven funds do high speed trading

 This shift began a couple of decades ago. Today’s markets can move faster than a human can react.

Another shift has been the degree to which passive investing through index funds and algorithmic trading through various quant funds have come to eclipse retail investing and dominate trading. 

A consequence of this is that to some degree it has mooted individual stock picking because when investors move in or out of index funds, the managers have to buy or sell the stocks held on a pro rata basis and not on individual merit.

Naked Capitalism 18May 2022

https://www.nakedcapitalism.com/2022/05/how-the-options-tail-has-come-to-wag-the-market-dog.html