Everyone is watching the same thing, looking for the same thing. Reacting the same way. Anyone else who is not, is getting 'trained' and corroded away to the point they fall into the funnel of the 'Market'. Algorithms have been programmed to look for the same things. Move with the market and you will be rewarded.
Wait until volatility picks up and there is a bear market. Let's see how well you "move with the market" then.
Easier said than done, I'm sure alot of people believe...The Trend is your Friend, and generally speaking it is... __Yet so many still fail. Show me a person who can predict and/or trade and manage the S&P 500, DOW charts, On a Daily basis -- or weekly, monthly...or any time frame, Not that many people could tame that beast, Maybe an alien on Neptune can, ET
Basically algorithms are reinforcing each other irrespective of anything else. Its a circular loop of self reinforcement. Its not about index funds. Its about trying to coattail the money flows implied by self reinforcing positive feedback loops.