I'll try. Price discovery means finding out the value of a stock by people bidding to sell and buy it. Historically, beating the stock market is hard to do, so one strategy is to just go along for the ride, buy a little of everything. This is what ETFs do. You're not bidding your guess of the value a company should have, you are just saying "hey, I'll pay what that other guy is willing to pay". Now, thats not a problem necessarily, but if the majority of people are not placing their own bids, and everyone is just saying I'll take what the market rate is, then the price of a stock isn't really tied to anything. This is the world we are in today. ETFs have become so massive, some of them are starting to be the majority shareholder of the companies in their portfolio. Now let's say our dear leader really tanks the economy and everyone rushes to sell their ETFs. The companies most effected by whatever policy fuckup are not the only ones that go down, the whole market will go down. Scary stuff.